CasterSoundboard - A soundboard for hot-keying and playing back sounds. (For podcasting)
SoundNode - SoundCloud desktop app (OS X, Windows, Linux)
JN Soundboard - An open-source hotkey soundboard program
Cumulus - A SoundCloud player that lives in your menubar.
Soundplant - Play sound files with the computer keyboard
SoundCloud - Enjoy music & follow favourite artists