Magic Music Visuals - Fully-customizable and highly responsive visuals for live and recorded audio & MIDI.
Linux Show Player - Sound player designed for stage productions
MilkDrop - 3D audio visualization plugin, compatible with WinAmp plugin API
QLab - QLab, Live show control for Mac OS X.
projectM - projectM is an LGPL'ed reimplementation of Milkdrop under OpenGL.
Trigger Audio and Video Playback - Audio and video cue player for broadcast and live performance.