Spotify - Map shows when two people play same song at same time
Until AM - DJ in your browser with this SoundCloud music mixer
Playlist Machinery - Tools that help you create & organize your Spotify playlists
Songlio - Free musical guessing game: race friends to name that tune
Magic Playlist - Get the playlist of your dreams based on a song
Playlistify - Make Spotify playlists from 1001tracklists & setlist.fm sets