Tabletop Audio - Tabletop Audio is an ambient game audio site.
Linux Show Player - Sound player designed for stage productions
ambient-mixer - Listen online to relaxing sound atmospheres, ambient music or chilling sound effects. You can even create and mix your own moods, all for free.
QLab - QLab, Live show control for Mac OS X.
Syrinscape - Immersive, dynamic sound effects and music for tabletop games
Cue Player - Cue Player software for theater sound and lighting