Thank You DJ - Personalized, Data-Driven experience for your guests.
Spotify - Map shows when two people play same song at same time
TrackStack - Easy Spotify playlist sharing and collaboration
Last.fm - The world's largest online music service. Listen online, find out more about your favourite artists, and get music recommendations, only at Last.fm
Playlist Machinery - Tools that help you create & organize your Spotify playlists
SoundCloud - Enjoy music & follow favourite artists