humit - A social networking app for music sharing and discovery.
Undrtone - Social layer on top of Spotify and Rdio from Scott Vener
Songlink - Share music with anyone.
PlaylistMap - Connect with Spotify playlist curators from around the world
Son.gg in Slack - Share music with your team in Slack
BeatSense - Discover great music hand-picked by real people, in a single click. FREE and in real-time!