CasterSoundboard - A soundboard for hot-keying and playing back sounds. (For podcasting)
Show Cue System - Show Cue Systems
Soundpad - Play sounds in voice chats in high digital quality.
Linux Show Player - Sound player designed for stage productions
Soundboard Studio - Soundboard Studio lets you take your podcast, live show, gig or performance to the next level.
QLab - QLab, Live show control for Mac OS X.