Another one to check out would be The Filter (http://www.thefilter.com) They also recommend music based on your existing collection as well as filling your iPod and creating playlists from your iTunes.

Kevin, If you’re interested in looking for music based of a profile of existing music you like then you should try Scouta (http://scouta.com). Scouta is a Perth based company and is doing really innovative stuff around tagging, sharing and seaching media of virtually any kind (typically audio and video). I’d recommend checking them out!