Programs

In no particular order
NameDescription
CD/DVD  
DixX to DVDCreates DVD files (VOB) from almost any source movie file. This is very basic: no menus, no subtitles, no second soundtrack. Use a DVD-burning program to burn the resulting files to a DVD or CD.
Deep BurnerDeep Burner - Full-featured CD burning program. The free version only burns at 2X spped.
ImageBurnMinimal CD and DVD burning program. This will burn your pre-made "image" file to a CD.
CDR ToolsCommand-line tools for working with CDs and DVDs
CDRTFEA GUI front-end for the open-source CDR Tools collection of command-line CD and DVD burning utilities.
Video  
MplayerCommand line open-source player and (more importantly) video encoder for almost every video format
MPUINice point-and-click Windows wrapper for MPlayer to view movie files
VLCFree cross-platform media player. It supports a large number of multimedia formats, without the need for additional codecs.
PocketDivxEncoderConverts most video files into Divx or Xvid AVI movie files. This is actually a fancy front-end for the MEncoder program!
VirtualDubFree video editing program. It can open multiple video formats, but saves only to AVI.
VirtualDubModSame as VirtualDub, but opens more file types.
Audio  
AudacitySound editor and recorder
CDexCD-Ripper, extracting digital audio data from an Audio CD. The application supports many Audio encoders, like MPEG (MP2,MP3), VQF, AAC encoders. See also http://sourceforge.net/projects/cdexos/
Codecs  
Microsoft CodecsSelect "Codecs Installation Packages" to get other codecs.
OGG CodecsPopular royaly-free new codecs pair (OGG Theora for video and OGG Vorbis for audio). Download the most recent EXE installer for Windows.
XVidExtremely popular MPEG codec also supports DivX
AC3FilterDecoding of AC3/DTS/MPEG1/2 Audio Layer I/II formats. Support of DVD, AVI/AC3, AVI/DTS, WAV/AC3 and WAV/DTS
ffdshowDirectShow and VFW codec for decoding/encoding many video and audio formats, including DivX and XviD movies using libavcodec, xvid and other opensourced libraries
Real AlternativeUse this if you want to play Real content, but don't want to install the full RealPlayer.
QuickTime AlternativeUse this if you want to play QuickTime content without installing QuickTime.
Compression  
7-ZipThe only decent full-featured free zip program out there.
SFX MakerAn unabashedly Christian SFX maker. Create a self-extractor from any zip file. Excellent as an installer. Very nice because it allows lots of customization. You might also want http://www.davidcornish.com/download/support.exe to do things like change the icons in the resulting sfx files.
Free ExtractorCreates SFX files (self-extracting zip files) that have the look and feel of a professional installation program.
UPXUPX is a free, portable, extendable, high-performance executable packer for several different executable formats. You want this if you store utilities on removable media.
Graphics  
GIMPGIMP is the GNU Image Manipulation Program. It is for such tasks as photo retouching, image composition and image authoring. See also http://gimp.org/
GimpShopGIMP, but with all the menus switched around so it acts just like PhotoShop. See also http://plasticbugs.com/
Photo Filtre PhotoFiltre is a complete image retouching program. It allows you to do simple or advanced adjustments to an image and apply a vast range of filters on it.
XNViewImage retouching program, multimedia viewer, browser and converter.
IrfanViewIrfanView is a very fast, small, compact and innovative FREEWARE (for non-commercial use) graphic viewer for Windows 9x/ME/NT/2000/XP/2003/Vista
Documents  
Open OfficeWhy pay for Microsoft Office when this does it all for free?
NVUHTML Editing program
PDF CreatorPDFCreator is a free tool to create PDF files from nearly any Windows application. Create PDFs from any program that is able to print.
Internet  
uTorrentThe smallest Bittorrent client around. Why use anything else?
UltraVNCUltraVNC 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.
System  
BartPEBart's PE Builder helps you build a "BartPE" (Bart Preinstalled Environment) bootable Windows CD-Rom or DVD from the original Windows XP or Windows Server 2003 installation/setup CD, very suitable for PC maintenance tasks. It will give you a complete Win32 environment with network support, a graphical user interface (800x600) and FAT/NTFS/CDFS filesystem support. Very handy for burn-in testing systems with no OS, rescuing files to a network share, virus scan and so on. This will replace any Dos bootdisk in no time!
NIST TimeIf your Windows machine can't keep it's clock right, try this program from the National Institute of Standards. Put it in your "Startup" folder and run it with a command like "nistime-32bit.exe once quiet -s60".
SymmTimeA more robust and configurable time synch program. You do NOT need to fill in the download form to download the software.
SysInternalsA collection of utilities so good, Microsoft bought the entire web site.
Silent DriveChange the AAM setting in your hard drive to make it run quieter.
EICARA harmless test file that all anti-virus programs are made to detect.
Playing with Linux  
KNOPPIXKNOPPIX is a bootable Live system on CD or DVD, consisting of a representative collection of GNU/Linux software, automatic hardware detection, and support for many graphics cards, sound cards, SCSI and USB devices and other peripherals. KNOPPIX can be used as a productive Linux system for the desktop, educational CD, rescue system, or adapted and used as a platform for commercial software product demos. It is not necessary to install anything on a hard disk.
UbuntuUbuntu is a community developed, linux-based operating system that is perfect for laptops, desktops and servers. It contains all the applications you need - a web browser, presentation, document and spreadsheet software, instant messaging and much more. The desktop CD allows you to try Ubuntu without changing your computer at all, and at your option to install it permanently later. This type of CD is what most people will want to use. You will need at least 192MB of RAM to install from this CD.
DSLBoot from a business card CD as a live linux distribution (LiveCD). Boot from a USB pen drive. DSL has a nearly complete desktop, and many command line tools. All applications are chosen with the best balance of functionality, size and speed. Damn Small also has the ability to act as an SSH/FTP/HTTPD server right off of a live CD.
UnxUtilsPowerful Linux/Unix utilities for your Windows system.
Programming  
ScriptomaticWhy write scripts when you can just copy and paste?
Digital MarsC, C++, and D compilers. Also an ECMA script (JavaScript) interpreter and compiler.
VB5 Control Creation EditionFree from MIcrosoft, but Microsoft no longer has it on their site. Use your favorite search engine to look for "vb5ccein.exe" or get it and supporting documents from the link I have here. Confirm you get 7,479,944 bytes and a CRC32 of 765798F7 regardless of where you get it.
VB .NET ExpressThe free version of .NET
QBASIC InterpreterEverything from DOS 6. All you want are the QBASIC.* files. Tips: Use "SYSTEM" as the last line of code in QBASIC files so they exit completely. Use the "/H" option when starting QBASIC so it starts in a larger screen.
QuickBASICMicrosoft's compiler for QBASIC. No longer available from Microsoft. Searching for "qb45.zip" yields several different sources, some of which are a copy of the install disks, while others are just the core executables. For reference, my QB.EXE file extracted from the original install disks is 278,804 bytes with a CRC32 of B08BC0FE.