Spotify - Map shows when two people play same song at same time
ODJO - DJ music mixer. play, mix, record & share
Playlist Machinery - Tools that help you create & organize your Spotify playlists
BeDJ - Marketplace of detailed mixing instructions to DJ sets
Magic Playlist - Get the playlist of your dreams based on a song
Playlistify - Make Spotify playlists from 1001tracklists & setlist.fm sets