Plug - Lightweight OSX player for Hype Machine
Heartbeat - Listen to music with your friends together, on Spotify
Poolsuite™ - The super-summer music player
Festify - Festify is a free Spotify-powered app that lets your guests choose which music should be played...
Spotify - Map shows when two people play same song at same time
Join My Playlist - Listen to music live together with your friends in Spotify.