Yahoo's Musicmatch Radio and Music Store have now launched for Windows XP Media Center Edition and are available via Online Spotlight. Free CD Quality Radio and more personalization features than other services- not a bad experience out of the gate. You'll quickly run into premium features that cost extra however a free 7-day trial is available and some features are still free.  Media Center owners, just visit Online Spotlight and click on the Musicmatch icon.  Of course, Musicmatch is also available in the Digital Media Mall in Windows Media Player as well.