MTV Overdrive is a broad band channel by MTV. You can watch it directly in your browser, or you can download a small plugin and integrate it into Windows Media Center Edition. I've been playing with it tonight, and it's just awsome. No commercials (at least not in the Media Center version), and you can browse a huge library of music videos. It supports playlists, and there is no registration to use the service! And best of all; it's free!