Spotify - Map shows when two people play same song at same time
Playlist Machinery - Tools that help you create & organize your Spotify playlists
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
Magic Playlist - Get the playlist of your dreams based on a song
SoundCloud - Enjoy music & follow favourite artists
tradiio - Reward-based music discovery app