Linux Show Player - Sound player designed for stage productions
JN Soundboard - An open-source hotkey soundboard program
QLab - QLab, Live show control for Mac OS X.
Soundplant - Play sound files with the computer keyboard
Cue Player - Cue Player software for theater sound and lighting
Soundboard Studio - Soundboard Studio lets you take your podcast, live show, gig or performance to the next level.