Magic Music Visuals - Fully-customizable and highly responsive visuals for live and recorded audio & MIDI.
Vinyl Music Player - A fork of Phonograph Music Player that "makes all Pro features free, as they used to be".
MilkDrop - 3D audio visualization plugin, compatible with WinAmp plugin API
VPlayer - VPlayer - a free music player for VKontakte.
projectM - projectM is an LGPL'ed reimplementation of Milkdrop under OpenGL.
RockPlayer - RockPlayer is a video player that supports nearly all formats.