Live365 - 5,000+ online radio stations run by real people, not generated by computers.
Spotify - Map shows when two people play same song at same time
Listen2MyRadio - Stop dreaming, start streaming. Free and premium Shoutcast and Icecast audio broadcasting.
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
Wohooo.net - Create Your Own Online Radio Station
SoundCloud - Enjoy music & follow favourite artists