100+ awesome free and open source applications

It has always amazed me quite how many incredible, varied and useful applications are available for free on the Internet.  Be it free, open source, web-based or merely passive trials - the number of top quality items on offer is huge.


The purpose of this list is to help people realise that the free and open source software communities are expansive and generous.  In these tense economic times, raising awareness of such projects is something I'm more than happy to do.  If you feel that I've missed something good off the list, please leave a comment at the bottom - I read absolutely every one.

Image, Image Editing and Graphics

GIMP – http://www.gimp.org
The GNU Image Manipulation Program is a Photoshop replacement that doesn’t have "quite" as much functionality but it’s excellent for free. It comes installed by default on many Linux distros and is also available in Windows. Worth a look.

Inkscape - http://www.inkscape.org/
Inkscape is an Open Source vector graphics editor, with capabilities similar to Illustrator, Freehand, CorelDraw, or Xara X using the W3C standard Scalable Vector Graphics (SVG) file format.

Paint.net - http://www.getpaint.net
A really good, lightweight alternative to Photoshop. It offers layers, unlimited undo, special effects and a wide variety of useful tools. The download is around 2mb too so absolutely worth a look – I use this when Photoshop is playing up.

XnView - http://perso.orange.fr/pierre.g/xnview/enhome.html
XnView is software to view and convert graphic files, apparently really simple to use and supports more than 400 graphics formats.

ImageMagick - http://www.imagemagick.org/script/index.php
A lesser known application but it offers the ability to "create, edit, and compose bitmap images. It can read, convert and write images in a variety of formats (about 100)". Use it to "translate, flip, mirror, rotate, scale, shear and transform images, adjust image colors, apply various special effects, or draw text, lines, polygons, ellipses and B?zier curves."

Irfanview - http://www.irfanview.com/
IrfanView is a very fast, small, compact and innovative freeware graphic viewer for Windows. IrfanView was the first Windows graphic viewer worldwide with Multiple (animated) GIF support. One of the first graphic viewers worldwide with Multipage TIF support. The first graphic viewer worldwide with Multiple ICO support.

Google Sketchup - http://sketchup.google.com/
SketchUp is a 3D modeling program designed for professional architects, civil engineers, filmmakers, game developers, and related professions. Sketchup may also be used to design buildings to be displayed on Google Earth. It was designed to be more intuitive, flexible, and easier to use than other 3D modeling programs, which often have steep learning curves.

Blender - http://www.blender.org/download/get-blender/
A 3D Studio Max alternative, very comprehensive and full-featured.

Artweaver - http://www.artweaver.de/index.php?en_version
Artweaver is a simple Freeware program for creative painting, i.e. Artweaver offers you all artistic effects which you need for your work. You can create sketches from photos and experiment with a wide range of brushes. The brush simulation is thereby so realistic as possible.

Office

OpenOffice – http://www.openoffice.org
It’s basically Microsoft Office so you need little else with this installed. It has MS Office support (in both reading and writing) so this fantastic suite is fully compatible.


Wink - http://www.debugmode.com/wink/
Wink is a freeware screen-capture and tutorial-creation program written by Satish Kumar. It supports many features such as input-based capture and text annotations. Navigation buttons can be added to any presentation and the bitmaps for all presentation controls can be edited. Wink also has multilingual support and can be used in English, French, German, Italian, Danish, Spanish, Serbian, Japanese, Brazilian Portuguese and Simplified/Traditional Chinese.

Scribus - http://www.scribus.net/
Scribus is an open-source program that brings award-winning professional page layout to Linux/Unix, MacOS X, OS/2 and Windows desktops with a combination of "press-ready" output and new approaches to page layout. Underneath the modern and user friendly interface, Scribus supports professional publishing features, such as CMYK color, separations, ICC color management and versatile PDF creation.

Google Documents - http://docs.google.com/
Google documents is a free service that simply requires registration in order to use it. You create Microsoft-Office-esq documents in an online environment and they store them on their servers. You can export them and save the files to your hard drive too. In addition, Google allows multiple user collaboration which means numerous people can all be working on the same document at the same time and it will update in real time. Very cool stuff.

Foxit - http://www.foxitsoftware.com/pdf/rd_intro.php
Foxit Reader is a free PDF document viewer and printer, with incredible small size (only 2.1 M download size), breezing-fast launch speed and amazingly rich feature set. Foxit Reader supports Windows 98/Me/2000/XP/2003/Vista. Its core function is compatible with PDF Standard 1.7.

Web and web development

Firefox - http://www.mozilla-europe.org/en/products/firefox/
Firefox is arguably the second most popular browser available (sitting behind the various Internet Explorers). It's extendable, customisable, secure and massively popular. You can develop plugins for it, other people develop plugins for it - it's just worth having.  You almost certainly already have it. 

Opera - http://www.opera.com
This is my personal browser of choice, sexy tabbed browsing, customisable, standards complient and fast. As they put it themselves: "The award-winning Opera Web browser The coolest, fastest, and most secure free Web browser available."

Opera web developer toolbar - http://operawiki.info/WebDevToolbar
The web developer toolbar is a menu and toolbar setup for Opera which brings together functions related to web development, validation services and links to standards and other documentation.

Amaya - http://www.w3.org/Amaya/
Amaya is a Web editor to create and update documents directly on the Web. Browsing features are seamlessly integrated with the editing and remote access features in a uniform environment. This follows the original vision of the Web as a space for collaboration and not just a one-way publishing medium. Amaya started as an HTML + CSS style sheets editor. Since that time it was extended to support XML and an increasing number of XML applications such as the XHTML family, MathML, and SVG. It allows all those vocabularies to be edited simultaneously in compound documents.

Notepad++ - http://notepad-plus.sourceforge.net/uk/site.htm
Notepad++ is a free source code editor (and Notepad replacement), which supports several programming languages, running under the MS Windows environment.

Kuler - http://kuler.adobe.com/
A very powerful colour-picking tool, allowing for the easy creation of colour schemes.

Aptana - http://www.aptana.com/
The Aptana IDE is a free, open-source, cross-platform, JavaScript-focused development environment for building Ajax applications. It features code assist on JavaScript, HTML, and CSS languages, FTP/SFTP support and a JavaScript debugger to troubleshoot your code.

Color Cop - http://colorcop.net
A very handy tool for capturing colours anywhere on your screen. Color Cop makes it quick and easy in those situations where you need to know what colour is being used.

Firefox web developer toolbar - https://addons.mozilla.org/en-US/firefox/addon/60
The Web Developer extension adds a menu and a toolbar to the browser with various web developer tools. It is designed for Firefox, Flock, Mozilla and Seamonkey, and will run on any platform that these browsers support including Windows, Mac OS X and Linux.

Internet Explorer Toolbar - [another long url]
The Microsoft Internet Explorer Developer Toolbar provides a variety of tools for quickly creating, understanding, and troubleshooting Web pages. This version is a preview release and behavior may change in the final release.

Firebug - http://www.getfirebug.com/
Firebug integrates with Firefox to put a wealth of web development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page.

Wave - http://wave.webaim.org/
With the demise of Watchfire Bobby and WebXact, WAVE has become a great automated online accessibility tool. Either link to a site, paste in the code or upload a file and it will give you a detailed breakdown of how accessible your work is.

JsUnit - http://www.jsunit.net/
JsUnit is a Unit Testing framework for client-side (in-browser) JavaScript. It is essentially a port of JUnit to JavaScript. Also included is a platform for automating the execution of tests on multiple browsers and mutiple machines running different OSs.

Xenu - http://home.snafu.de/tilman/xenulink.html
Xenu’s Link Sleuth (TM) checks Web sites for broken links. Link verification is done on "normal" links, images, frames, plug-ins, backgrounds, local image maps, style sheets, scripts and java applets. It displays a continously updated list of URLs which you can sort by different criteria. A report can be produced at any time.

Vischeck - http://www.vischeck.com/vischeck/vischeckURL.php
Vischeck is a way of showing you what things look like to someone who is color blind. You can try Vischeck online- either run Vischeck on your own image files or run Vischeck on a web page. You can also download programs to let you run it on your own computer.

Feng GUI - http://www.feng-gui.com/
Find out how people View your website or image and which areas are getting most of the attention. The ViewFinder Heatmap service, is an artificial intelligence service which simulates human visual attention and creates an attention heatmap.

Fiddler - http://www.fiddlertool.com/fiddler/
Fiddler is a HTTP Debugging Proxy which logs all HTTP traffic between your computer and the Internet. Fiddler allows you to inspect all HTTP Traffic, set breakpoints, and "fiddle" with incoming or outgoing data. Fiddler includes a powerful event-based scripting subsystem, and can be extended using any .NET language.

browsershots.org - http://browsershots.org/
Browsershots.org is a free open-source online service providing screenshots of your web site in a multitude of different browsers. It is not as advanced as BrowserCam but a fantastic tool none the less.

Expresso 2.1 - http://www.ultrapico.com/Expresso.htm
Expresso is useful tool for learning how to use regular expressions and for developing and debugging regular expressions prior to incorporating them into your code. It provides a very cut down version of RegexBuddy but most importantly it is simple to use and free.

ColorJack - [very long url]
ColorJack is an amazing online application providing users with the ability to match colours that work well together. Perfect for those developers who struggle to get a good colour scheme together.

Development Applications (IDE's)

Eclipse - http://www.eclipse.org/
Eclipse is an open source community whose projects are focused on building an open development platform comprised of extensible frameworks, tools and runtimes for building, deploying and managing software across the lifecycle. It’s quite hardcore in my personal opinion so certainly not one for beginners.

NetBeans - http://www.netbeans.org/
All the tools software developers need to create cross-platform Java desktop, enterprise and web applications. Runs on Windows, Linux, MacOS, as well as Solaris. I never got on well with NetBeans but it is a good application, just not one I choose.

Geany - http://geany.uvena.de/
Geany is a text editor using the GTK2 toolkit with basic features of an integrated development environment. It was developed to provide a small and fast IDE, which has only a few dependencies from other packages. It supports many filetypes and has some nice features

Code::Blocks - http://www.codeblocks.org/
A free c++ IDE built to meet the “most demanding needs of its users”.

SharpDevelop - http://www.sharpdevelop.net/OpenSource/SD/Default.aspx
A free IDE for C#, VB.net and Boo projects on Microsoft’s .NET platform.

Zend Studio - http://www.zend.com/products/studio
While not strictly free, once your trial period expires only a subset of the functionality gets turned off. The really useful bits such as code compete, syntax suggestion and its own SVN client remain fully operational. In reality the only stuff I've found frustrating is that the rename functionality is removed unless you buy the license. Alternatively you could obtain Zend certification and in turn receive a free license - your call.

Operating Systems

Ubuntu - http://www.ubuntu.com
The most popular Linux distro at the moment - offering astonishing performance, usability and support (from a massive online community) all for free.

PCLinuxOS - http://www.pclinuxos.com/
One of my favourite Linux releases; PCLinuxOS is very different to Ubuntu but powerful and usable in equal measures. I find it a lot more intuitive but purely though personal preference. It too is supported by a healthy community.

Fedora - http://fedoraproject.org/
I'm not a Fedora user but there are an awful lot of them. Fedora was the daddy long before Ubuntu appeared on the scene and therefore it inherits a lot of excellent features from how long these guys have been doing it. Excellent software, strong communities and worth a look. This is Linux too incase you didn't know.

openSUSE - http://www.opensuse.org/
Quoted as being one of the more fully featured, usable editions of Linux - openSUSE has a lot of users and is one of the major players in the scene today.

Lots more Linux! - Distrowatch has info on lots more
Linux is free and it is becoming a viable alternative to Windows these days; here is Distrowatch - a site that links to reviews on each release as well as offering a brief description, background and links.

Video Playback and Editing

Media Player Classic - [long url]
Amazingly lightweight and incredibly durable - MPC succeeds where most others fail. It really will play anything and doesn’t even need installing.

MPlayer - http://www.mplayerhq.hu/design7/news.html
A decent video player for Linux.

Kaffeine - http://kaffeine.kde.org/
Another decent video player for Linux (KDE).

Apple Quicktime - http://www.apple.com/quicktime/download/
If you've managed to get this far through life without experiencing Quicktime, then you're probably suffering from Alzheimer's. Quicktime is a commonly used media playback application (you probably already have it installed).

VLC Media Player - http://www.videolan.org/vlc/
A very popular application; a highly portable multimedia player for various audio and video formats. It will play just about anything too.

VirtualDub - http://www.virtualdub.org/
It's a bit like a really cut down, free version of Adobe Premier... VirtualDub is mainly geared toward processing AVI files, although it can read (not write) MPEG-1 and also handle sets of BMP images. Worth a look.

Youtube - http://www.youtube.com
Youtube is maybe an odd choice to put into the video playback area but there's a good reason for it. You can upload your videos to Youtube quite happily for free and there are hundreds upon thousands of hours of footage on there. From the illegal to the completely random Youtube has more video playback options than your wildest dreams.

CamStudio - http://camstudio.org/
This is actually a screencasting utility so it doesn't really fit into this category very well... CamStudio is able to record all screen and audio activity on your computer and create industry-standard AVI video files and using its built-in SWF Producer can turn those AVIs into lean, mean, bandwidth-friendly Streaming Flash videos (SWFs).

Audio

Audacity - http://audacity.sourceforge.net/
Audacity is free, open source software for recording and editing sounds. It is available for Mac OS X, Microsoft Windows, GNU/Linux, and other operating systems.

Songbird - http://www.songbirdnest.com/
Songbird is a desktop media player mashed-up with the Web. Songbird is committed to playing the music you want, from the sites you want, on the devices you want, challenging the conventions of discovery, purchase, consumption and organization of music on the Internet. Songbird is a popular alternative to Apple's iTunes.

iTunes - http://www.apple.com/itunes/download/
iTunes is one of the world's most popular audio applications, although it breaks through that label by allowing users to purchase media online, schedule podcasts, view artist information etc. Very popular.

Winamp – http://www.winamp.com
While not open source, it is free and very good indeed. Far better than iTunes in my personal opinion.

MusikCube - http://www.musikcube.com/
Another iTunes alternative - very good, just really a matter of personal taste in the end.

Amarok - http://amarok.kde.org/
This is one of the best media players I have ever encountered, unfortunately it's purely limited to Linux (KDE environments only) so it's beyond the reach of Windows users and the "Ubuntu mainstream". It's amazing though and I highly recommend it.

Foobar2k - http://www.foobar2000.org
Foobar2000 is an advanced audio player for the Windows platform. Some of the basic features include full unicode support, ReplayGain support and native support for several popular audio formats.

Anti-Virus and Security

AVG - http://free.grisoft.com/doc/1
A popular and comprehensive, free anti-virus application. I use it. Simple.

Avast! Home edition - http://www.avast.com/eng/avast_4_home.html
Also quite popular and available for free.

Antivir - http://www.free-av.com/
A free antivirus application (although it doesn't detect spyware). It apparently has one of the best detection rates out of the free antiviruses on offer.

Clamwin - http://www.clamwin.com/
A free antivirus with a high detection rate for infected files. It's not very invasive because it doesn't do on-access virus scanning - you specifically need to say which folders to scan. This is both good and bad - good if you're IT savvy because you don't need on access scanning because you're not stupid enough to do "dodgy" things unprotected. It's bad if you're not because it won't tell you that there's a problem until you tell it to look.

Comodo Firewall - http://www.comodo.com/products/free_products.html
Comodo Firewall, rated by PC Magazine Online as an Editor's Choice, constantly monitors and defends your PC from internet attacks. It's easy to install and use and passes the industry's most stringent firewall "leak" tests.

Windows Defender - http://www.microsoft.com/athome/security/spyware/software/default.mspx
Windows Defender is a free program that helps protect your computer against pop-ups, slow performance, and security threats caused by spyware and other unwanted software. It features Real-Time Protection, a monitoring system that recommends actions against spyware when it's detected and minimizes interruptions and helps you stay productive. It's Microsoft though, but good enough I suppose. Not my sort of thing but a lot of people use it.

Spyware Terminator - http://www.spywareterminator.com/
Does exactly what it says on the tin. Spyware gets terminated. End of.

Arovax Antispyware - http://www.arovaxantispyware.com/
Another free antivirus, another one that does what it says on the tin.

Downloading and Download Managers

Orbit - http://www.orbitdownloader.com/
Orbit Downloader, leader of download manager revolution, is devoted to new generation web (web2.0) downloading, such as video/music/files from Myspace, YouTube, Imeem, Pandora, Rapidshare. And to make general downloading easier and faster.

Utorrent - http://www.utorrent.com/
The single best torrent application available. I've used many many alternatives and this is the single greatest one around. It has a tiny footprint (only a few Kb of RAM) and doesn't need installing. Excellent.

Filezilla - http://filezilla-project.org/
An awesome FTP client; the one I use the most on a day-to-day basis.

SmartFTP - http://www.smartftp.com/
SmartFTP is an FTP (File Transfer Protocol) client which allows you to transfer files between your local computer and a server on the Internet. With its many basic and advanced features SmartFTP also offers secure, reliable and efficient transfers that make it a powerful tool.

eMule - http://www.emule-project.net/home/perl/general.cgi?l=1
eMule is one of the biggest and most reliable peer-to-peer file sharing clients around the world. Thanks to it's open source policy many developers are able to contribute to the project, making the network more efficient with each release.

Azureus - http://azureus.sourceforge.net/
One of the most popular torrent clients available, this Java built monster does the job very well. My gripe with it is that it munches it's way through your RAM at an alarming rate (being a Java application). Good though, just a bit hungry for machines are left online 24/7/365 like mine is.

Flashget - http://www.flashget.com/en/download.htm
FlashGet is a leading download manager and has the highest amount of users on the internet. It uses MHT(Multi-server Hyper-threading Transportation) technique, supports various protocols and has excellent document management features. FlashGet is a freeware without any adware or spyware.

Freedownloadmanager - http://www.freedownloadmanager.org/
FDM is a powerful, easy-to-use and absolutely free download accelerator and manager. Moreover, FDM is 100% safe, open-source software distributed under GPL license.

Remote Access

rDesktop - http://www.rdesktop.org/
rdesktop is an open source client for Windows NT Terminal Server and Windows 2000/2003 Terminal Services, capable of natively speaking Remote Desktop Protocol (RDP) in order to present the user's NT desktop. Unlike Citrix ICA, no server extensions are required.

TightVNC - http://www.tightvnc.com/
TightVNC is a free remote control software package derived from the popular VNC software. With TightVNC, you can see the desktop of a remote machine and control it with your local mouse and keyboard, just like you would do it sitting in the front of that computer.

UltraVNC - http://www.uvnc.com/
UltraVNC is a powerful, easy to use and free software that can display the screen of another computer (via internet or network) on your own screen. The program allows you to use your mouse and keyboard to control the other PC remotely. It means that you can work on a remote computer, as if you were sitting in front of it, right from your current location.

LogMeIn - https://secure.logmein.com/home.asp?lang=en
Their website states "20 million users trust LogMeIn solutions for remote support, access & backup" so that probably says enough.

Putty - http://www.chiark.greenend.org.uk/~sgtatham/putty/
I wasn't quite sure where to put Putty but I was certain that it needed to be in this list - I use it on a daily basis for remoting into servers, connecting to MySQL databases etc... It's simple and a vital application.

Useful Applications that don't get their own category

CDBurnerXP - http://cdburnerxp.se/
This is an amazingly useful, free burner application. Although I don't believe it works on Vista yet...

AutoHotKey - http://www.autohotkey.com/
AutoHotkey is a free, open-source utility for Windows. With it, you can automate almost anything by sending keystrokes and mouse clicks. You can write a mouse or keyboard macro by hand or use the macro recorder. It's a very useful application and worth a look - especially good for those with limited finger dexterity - because it can automate short-hand typing into long-hand (if set up correctly).

Visuwords - http://www.visuwords.com/
This isn't an installable application but rather a very cool online dictionary/thesaurus. You enter a word and it graphically models that word, with various uses and synonyms mapped around it like a mind-map. A very cool free "service" for writers.

Notepad2 - http://www.flos-freeware.ch/notepad2.html
It's basically notepad but more helpful for doing code and stuff in. It's just notepad with more functionality; which makes life a bit easier. Code highlighting is handy and it doesn't need installing and it doesn't touch your registry. It's safe, simple and very useful.

VIM - http://www.vim.org/
Vim is an advanced text editor that seeks to provide the power of the de-facto Unix editor 'Vi', with a more complete feature set. It's useful whether you're already using vi or using a different editor.

Synergy - http://synergy2.sourceforge.net/
Synergy lets you easily share a single mouse and keyboard between multiple computers with different operating systems, each with its own display, without special hardware. It's intended for users with multiple computers on their desk since each system uses its own monitor(s).

Quicksilver - http://qsapp.com/
When opened, it will create a catalog of applications and some frequently used folders and documents. Activate it, and you can search for and open anything in its catalog instantly. The search is adaptive, so Quicksilver will recognize which items you are searching for based on previous experience. It also supports abbreviations, so you can type entire words, or just fragments of each. When not in use, Quicksilver vanishes, waiting for the next time you summon it. OSX only though...

7Zip - http://www.7-zip.org/
WinRAR and Winzip need paying for (eventually), 7zip is free and does the same thing. That's it really.

JZip - http://www.jzip.com/
Create, open and extract Zip, TAR, GZip and 7-Zip. Open and extract from RAR and ISO. No surprises then.

Google Desktop - http://desktop.google.com/
This is a surprisingly useful application to have. It has desktop search (it searches through all your files and folders for what you've searched for, including your email - which is VERY useful). It will also do RSS updates straight to your desktop, news updates, weather information, to-do lists, notepads, you name it. It does it all.

GNU Cash - http://www.gnucash.org/
GnuCash is personal and small-business financial-accounting software, freely licensed under the GNU GPL and available for GNU/Linux, BSD, Solaris, Mac OS X and Microsoft Windows. This powerful little app manages scheduled calculations, graphing and any number of things that those too lazy to master a spreadsheet will find useful.

Communications

Skype - http://www.skype.com/intl/en-gb/
Make calls from your computer — free to other people on Skype and cheap to phones and mobiles around the world. Enough said really.

Thunderbird - http://www.mozilla-europe.org/en/products/thunderbird/
Mozilla's alternative to Outlook. It's just brilliant, possibly the best email client I've ever used; which I use on a day-to-day basis.

Pidgin - http://www.pidgin.im/
Pidgin is a multi-protocol Instant Messaging client that allows you to use all of your IM accounts at once. Pidgin can work with: AIM, Bonjour, Gadu-Gadu, Google Talk, Groupwise, ICQ, IRC, MSN, MySpaceIM, QQ, SILC, SIMPLE, Sametime, XMPP, Yahoo! and Zephyr.

mIRC - http://www.mirc.com/
A little old school now but IRC is still going strong and this is the most popular client in the world.

Trillion - http://www.ceruleanstudios.com/
Trillian is a proprietary multiprotocol instant messaging application for Windows created by Cerulean Studios that can connect to multiple IM services, such as AIM, ICQ, Windows Live Messenger, Yahoo! Messenger, IRC, Novell GroupWise Messenger, Bonjour, Jabber, and Skype networks (the latter four with Trillian Pro which allows for additional plugins).

Servers, techie stuff

Apache - http://www.apache.org/
Apache really doesn't need any explanation as it is the god of the Internet. I'll just include this and no further deriviatives such as Tomcat/JBOSS/whatever.

XAMPP - http://www.apachefriends.org/en/xampp.html
XAMPP is an easy to install Apache distribution containing MySQL, PHP and Perl. XAMPP is really very easy to install and to use - just download, extract and start. It comes for Windows, OSX, Solaris and Linux.

MySQL community server - http://dev.mysql.com/downloads/mysql/5.0.html
This version of the MySQL database server is free, quite obvious really.

PostgreSQL - http://www.postgresql.org/
PostgreSQL is a powerful, open source relational database system. It has more than 15 years of active development and a proven architecture that has earned it a strong reputation for reliability, data integrity, and correctness. It runs on all major operating systems. I used this for the majority of University - it's excellent.

Nagios - http://www.nagios.org/
Nagios is a host and service monitor designed to inform you of network problems before your clients, end-users or managers do. It has been designed to run under the Linux operating system, but works fine under most *NIX variants as well. The monitoring daemon runs intermittent checks on hosts and services you specify using external "plugins" which return status information to Nagios. When problems are encountered, the daemon can send notifications out to administrative contacts in a variety of different ways (email, instant message, SMS, etc.). Current status information, historical logs, and reports can all be accessed via a web browser.

EasyPHP - http://www.easyphp.org/?lang=en
EasyPHP is a complete software package allowing to use all the power and the flexibility that offers the dynamic language PHP and the effecient use of databases under Windows. Package includes an Apache server, a MySQL database, full PHP as well as easy development tools for your web site or your applications. This is comparable to XAMPP (see above).

WINE - http://winehq.org/
Again, one I wasn't quite sure what to classify it as (it's definitely NOT an emulator though, heh). Wine is a software application which aims to allow Unix-like computer operating systems on the x86 architecture to execute programs that were originally written for Microsoft Windows. Wine also provides a software library known as Winelib which developers can compile Windows applications against in order to port them to Unix-like systems.

Games

FreeCiv – http://www.freeciv.org/index.php/Freeciv
A free development of the popular Civilisation games created by Sid Meier.

FreeCol - http://www.freecol.org/
Exactly the same but for Colonisation.


Also here is a massive list of open source games for Windows that's absolutely worth checking out.


This list of 100+ applications barely scratches the surface of what is out there; but it's a start.  If you think I've missed something awesome off this list, let me know via email or in a comment below and I'll add it to the next iteration of this list.  I hope this was useful to at least one person.