Defiler Pack	Collection of media codecs. Freeware. Support for all the good codecs out there, such as divx and xvid plust a few others.
CDex	CD ripper and format converter.
CDrSoft	Site offering various codecs. CD & DVD Tools for download
Winamp	This has to be the best MP3 player. Supports many formats including video.
Autorun.inf Editor	Easily create the special file that causes programs to run automatically when a CD is inserted.