PlaylistMap - Connect with Spotify playlist curators from around the world
Momixa - Pick two songs and get the perfect mix
Undrtone - Social layer on top of Spotify and Rdio from Scott Vener
Liveset Database - Database site with tracklists from Dj sets
SoundCloud Charts - The most played tracks on SoundCloud this week
FIEND.fm - "Hot or Not" for music discovery: 2 hrs of tracks in 2 mins