Openwhyd - Collect and Share the tracks you love.
SoundCloud - Enjoy music & follow favourite artists
Tunit.fm - the largest FREE music listening platform on the planet.
yungcloud - "the world's leading underground music streaming service."
Tenory - Social community for discovering and sharing everything about music.
Artrezor.com - New beta social network for sound lovers, including waveform player and uploads. And it's free.