This is a collection of links and recommendations posted by other users.. I've only combined them to help clean up the stickies section. Thank you very much to andri12 for their original "List of Useful Programs" thread. Please, feel free to reply with your own recommendations... however, please try to only recommend programs that are free of charge. I will add to the list your recommendations whenever I have the chance.
Archiving (used for opening .rar and .zip files)
Winrar (how-to here)
7zip
Web Browsers
Mozilla Firefox
Google Chrome
Opera
Safari
AntiVirus Software
avast!
AVG
Avira
Microsoft Security Essentials
Mediaplayers
Windows Classic MediaPlayer
VideoLan (VLC)
KMPlayer
Winamp (best for MP3 and FLAC)
Video Codecs
K-lite (comes with Windows Classic Mediaplayer)
CCCP
Shark007's Win7Codecs
Koepi's XVID Codec
Image Editing
The Gimp
Paint.net
Word Processing
OpenOffice
AbiWord
Image Mounting
DAEMONtools Lite (tutorial here)
Other
Japanese Language Pack (Windows XP)
File Sharing Sites Downloader Cheat (more info here)
CDisplay (comic book/manga reader)
Picasa (image organizer and viewer)
NitroPDF (alternative to Adobe Acrobat)
Sandboxie (isolate potentially harmful files for safe removal)
DomDom Manga Downloader