Linux Show Player - Sound player designed for stage productions
Magic Music Visuals - Fully-customizable and highly responsive visuals for live and recorded audio & MIDI.
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.
Kauna - Kauna is a music visualizer. Kauna renders any sound reproduction in system.