BandNext - Discover bands that sound similar to artists you already love with BandNext. A single click saves your results to a Youtube playlist.
Musicroamer - A visual Pandora for discovering new music
22tracks - DJ curated Spotify playlists on iOS
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.
8tracks 3.0 (iOS) - Refreshingly human music playlists
Spotify - Map shows when two people play same song at same time