Last.fm
Last.fm is a music engine based on a massive collection of Music Profiles. Each music profile belongs to one person, and describes their taste in music. Last.fm uses these music profiles to make personalized recommendations, match you up with people who like similar music, and generate custom radio stations for each person.

mystrands
Our music recommendation technology is based on the collective expertise of our entire music community. We carefully track the music our members listen to, what songs they play together, what songs they add to playlists. The result are recommendations of songs that “fit” not because they are audio clones, but because they just sound right.

Pandora
Pandora is a music discovery service designed to help you find and enjoy music that you'll love. It's powered by the Music Genome Project, the most comprehensive analysis of music ever undertaken. Just tell us one of your favorite songs or artists and we'll launch a streaming station to explore that part of the music universe.