Partyhero - Pass your friends the aux!
Muzzy - it’s a tiny and gorgeous iTunes companion that lives on your menu bar. For Mac OSX, its free!
Heartbeat - Listen to music with your friends together, on Spotify
SpotiMy - Play/Pause and Next/Previous functions for Spotify directly on your Menu Bar!
TuneMeet - Chat with people who are listening to the same song
Tabler - Admin panel made simple