Battle of the music streaming subscription or ad revenue sites... what if any of these sites do you use and why?

MOG - Discover People Through Music and Music Through People

Pandora Internet Radio - Find New Music, Listen to Free Web Radio

Spotify – A world of music

Music, Downloads, Music Videos, Lyrics and Photos - Rhapsody

Grooveshark - Listen to Free Music Online - Internet Radio - Free MP3 Streaming