Spotify - Map shows when two people play same song at same time
Tempso - Finally a place for classical music online!
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
Concertmaster - Classical music front-end for Spotify
SoundCloud - Enjoy music & follow favourite artists
Classical Page - Email notifications for live classical music near you