Gnoosic - Even if you don't know what you are looking for - gnod will find it.
Musicroamer - A visual Pandora for discovering new music
BandNext - Discover bands that sound similar to artists you already love with BandNext. A single click saves your results to a Youtube playlist.
Songstack - Swipe to discover new music for Spotify
Music-Map - The Music-Map is the Tourist Map of Music, part of Gnod, the Global Network of Discovery.
mixmello - mixmello is a free, open source tool to create remixed versions of your favourite playlists.