Gnoosic - Even if you don't know what you are looking for - gnod will find it.
Openwhyd - Collect and Share the tracks you love.
BandNext - Discover bands that sound similar to artists you already love with BandNext. A single click saves your results to a Youtube playlist.
HipHopEarly - HipHopEarly developed by Idle Media Inc.
Musicroamer - A visual Pandora for discovering new music
Music Smasher - Find any song. Music Smasher searches Spotify, Rdio, SoundCloud, Bandcamp, and YouTube.