Napster has caught on the mobile music app, and decided (no matter how late) that it might be the next big thing. They've launched an iPhone and Android app. It's a streaming-only service that also allows for downloading of tracks, so that you can still play them offline. The Napster streaming service is a subscription that will cost you a competitive $10 a month.
It also integrates with the Billboard charts, just in time for the relevance of the Billboard charts during the last century. Why not move on the the newer Big Champagne Ultimate Chart? The Napster subscription gets them into the game, but later than other services like MOG, and offers the same thing as those services, with no new features and the same price.