BandNext - Discover bands that sound similar to artists you already love with BandNext. A single click saves your results to a Youtube playlist.
Music-Map - The Music-Map is the Tourist Map of Music, part of Gnod, the Global Network of Discovery.
Songstack - Swipe to discover new music for Spotify
Tempso - Finally a place for classical music online!
Music Walker - Explore and play (via YouTube) songs similar to a seed song.
Concertmaster - Classical music front-end for Spotify