FIEND.fm - "Hot or Not" for music discovery: 2 hrs of tracks in 2 mins
BandNext - Discover bands that sound similar to artists you already love with BandNext. A single click saves your results to a Youtube playlist.
Pacemaker - Create and share mixtapes with friends
Musicroamer - A visual Pandora for discovering new music
Boil the Frog - Create a seamless playlist between any two artists
stats.fm - With the click of a button you'll be logged with your Spotify account and you'll instantly gain access to a valhalla of cool stats and insights.