Playlist Machinery - Tools that help you create & organize your Spotify playlists
Openwhyd - Collect and Share the tracks you love.
Heartbeat - Listen to music with your friends together, on Spotify
SoundCloud - Enjoy music & follow favourite artists
Partyhero - Pass your friends the aux!
Music Smasher - Find any song. Music Smasher searches Spotify, Rdio, SoundCloud, Bandcamp, and YouTube.