Great Free Software
The following is a categorised list of the free/open source software I use.
Many of these programs are the best you can get - even when compared to commercial alternatives. If you like any of them, don't forget to support them and if you can donate to the project.
Database
| SQLDeveloper | Oracle SQL Client |
| SQLTools++ | Oracle SQL Client |
| Statement Tracer for Oracle | Monitor/trace SQL executed by an application |
| Tora | Toad like database tool |
Desktop
| AutoHotKey | Create custom keyboard macros & shortcut keys |
| ClipX | Clipboard Manager/History |
| DexPot | Virtual desktops |
| FileMenuTools | Explorer Extension - Right-Click Menu Shortcuts |
| Find and Run Robot | Application Launcher |
| Launchy | Application Launcher |
| RocketDock | Mac OSX-like application launcher taskbar |
| TaskSwitchXP | Alt-Tab Task Switcher Replacement for XP |
| VistaSwitcher | Alt-Tab Task Switcher Replacement for Vista/7 |
Development
| Aptana Studio | A fantastic web development IDE with Ruby on Rails support |
| AstroGrep | Free/Open Source Portable GREP GUI |
| BareTail | Windows Tail GUI (monitor log file changes) |
| JDeveloper | Oracle's Java Development IDE |
| Joomla | Open Source Content Management System |
| Large Text File Viewer | File Viewer supports very large files |
| NetBeans IDE | Java IDE (also supports Ruby on Rails) |
| NotePad++ | Text Editor |
| Notepad2 | Basic Text Editor / Notepad Replacement |
| PSPad | Text Editor |
| SlikSVN | Windows SVN client |
| TortoiseGit | Windows Git GUI |
| TortoiseSVN | SVN GUI client for Windows |
| WinMerge | File and Directory Comparison |
Graphics
| FastStone Capture | Flexible Screenshot Capture Tool |
| Inkscape | Vector based (SVG) graphics editor similar to Illustrator |
| Paint.NET | Photo/Image Editor (supports layers) |
| PhotoFiltre | Photo/Image Editor |
| PicPick | Screen capture, Color Picker, and other Tools in One |
Internet
| DropBox | Online Storage and File Management |
| FileZilla | FTP Client |
| Firefox | Web Browser |
| Iron | Web Browser (Google Chrome alternative) |
| Opera | Web Browser |
| Pidgin | Instant Messenging Client |
| PuTTY CM | PuTTY Connection Manager |
| PuTTY Tray | SSH Client |
| SuperPutty | Tabbed PuTTY sessions |
| Thunderbird | Email Client |
| uTorrent | Bittorrent Client |
| WinSCP | FTP/SCP client |
Multimedia
| Audacity | Audio Editor |
| DVDFlick | DVD Authoring Software |
| DVDShrink | Rip DVDs to other formats |
| Handbrake | Multimedia Converter (including for portable devices) |
| Media JukeBox | MP3 Player/Music Management Software |
| VirtualDub | Video capture and processing |
| VLC | Multimedia (video/audio) Player |
Office
| FreeOCR | OCR tool - works on scanned input, images and PDF documents |
| Foxit | PDF Reader |
| GNUCash | Accounting and financial management software |
| OpenOffice | Office Suite |
| PDF Creator | Virtual PDF Printer |
| WorkRave | Reminds you to take regular breaks |
Operating Systems
| CentOS | Open Source Enterprise Linux |
| Xubuntu | Lightweight version of Ubuntu using Xfce |
Productivity
| Evernote | Take notes and synchronise them online and with mobile devices |
| FreeMind | Mind Mapping Tool |
| GeeTeeDee | GeeTeeDee Todo List Manager |
| The Guide | Outliner (store hierarchical/tree based notes) |
| Wunderlist | Todo list manager that can synchronise online and to mobile devices |
| XMind | Excellent Mind Mapping Software - Eclipse Based |
Security
| avast! | Antivirus |
| AVG Free | Antivirus |
| ClamWin | Antivirus |
| KeePass | Password Manager |
| PeerGuardian | Privacy/P2P IP Blocker |
| TrueCrypt | Disk Encryption |
Servers
| FileZilla Server | FTP Server for Windows |
| FreeSSHd | Simple, free SSH server for Windows |
| WAMP | Windows Apache-MySQL-PHP Server |
| XAMPP | Portable Apache-MySQL-PHP-Perl Devlopment Server |
System
| Autoruns | Startup Manager |
| 7-zip | File Compression |
| CCleaner | System & Windows Registry cleaner |
| CPU-Z | CPU/Motherboard/RAM/Graphics Card Identification Tool |
| Defraggler | Disk Defragmentation Tool |
| Disktective | Disk space reporting tool |
| Git for Windows | Git for Windows including Git Bash |
| ImgBurn | Burns and Creates ISO Images |
| InfraRecorder | CD/DVD Burning Software |
| JKDefrag | Disk Defragmentation Tool |
| PhotoRec (TestDisk) | Recovers data from unreadable disks (CDs, HDD, USB, Memory Cards etc) |
| Process Explorer | Task Manager |
| Recuva | Recovers deleted files |
| ReNamer | Flexible File/Folder Batch Renaming Tool |
| TeraCopy | Speeds up file copying/moving in Windows |
| TweakUI | Tweaks Windows System Settings |
| UnxUtils | Native Windows binaries of Unix command line tools |
| WinCDEmu | Mounts ISO, CUE, BIN, RAW, IMG images as virtual CD/DVD drives |
Virtualization
| VirtualBox | Free virtualization software from Sun |