Openwhyd - Collect and Share the tracks you love.
Bandlab - Capture, nurture, and collaborate on song ideas in the cloud
SoundClick - SoundClick is a music-based social community.
AMPLI.FI - Live online music community. Twitch for tunes.
Music Smasher - Find any song. Music Smasher searches Spotify, Rdio, SoundCloud, Bandcamp, and YouTube.
Krue - Twitch for music: live streams from amazing musicians