PlaylistMap - Connect with Spotify playlist curators from around the world
Songlink - Share music with anyone.
Undrtone - Social layer on top of Spotify and Rdio from Scott Vener
humit - A social networking app for music sharing and discovery.
SoundCloud Charts - The most played tracks on SoundCloud this week
aux.app - A free web-based music platform to play music from other popular online streaming services.