AMPLI.FI - Live online music community. Twitch for tunes.
Openwhyd - Collect and Share the tracks you love.
Bandlab - Capture, nurture, and collaborate on song ideas in the cloud
Zoff - Collaborate on a live music and video playlist with your friends.
Blattarco - Creative self-developement for musicians of all level.
SoundCloud - Enjoy music & follow favourite artists