Kauna - Kauna is a music visualizer. Kauna renders any sound reproduction in system.
Plane9 - Plane9 is a revolutionary 3d visualizer where you never have to settle for just one view ever again.
MilkDrop - 3D audio visualization plugin, compatible with WinAmp plugin API
R4 - R4 is a standalone OpenGL accelerated program (created by Gordon Williams of RabidHaMsTeR.
projectM - projectM is an LGPL'ed reimplementation of Milkdrop under OpenGL.
Magic Music Visuals - Fully-customizable and highly responsive visuals for live and recorded audio & MIDI.