Spotify - Map shows when two people play same song at same time
SoundNode - SoundCloud desktop app (OS X, Windows, Linux)
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
Cumulus - A SoundCloud player that lives in your menubar.
SoundCloud - Enjoy music & follow favourite artists
Pandora - Pandora Radio is a free (ad-supported) internet radio founded in 2000.