www.microsoft.com information about WindowMedia format

www.divx.com DivX homepage

FFDShow is an excellent decoder of many video formats (MPEG4, DivX3,4 and 5, XVid, WMV 1...)

Ogg DSF - The Ogg Vorbis DirectShow filter collection from Tobias homepage

SlyDiman's homepage - Fastest 10-band equalizer (DirectShow DMO Audio Effect filter)

www.mp3.com well known site about mp3, you can download some sample mp3 files, too