Yet another player is entering the growingly-crowded mobile music market: Thumbplay. Traditionally, Thumbplay has stuck with ringtones from licensed artists, but they’re moving into full MP3 downloads. Essentially, the app for BlackBerry will sync up with your browser-based Thumbplay account to track favourites, playlists, and purchases, and allow you to either stream tunes over Wi-Fi or 3G, with the additional option to store locally for offline use. Throw in a dash of iTunes playlist syncing, and Bob’s your uncle. The app itself acts as the media player, so you might have some trouble with native shortcuts, but other than that, it looks like this mobile music store is about as good as any other, especially with all of their established licensing relationships. $9.99/month will get you all-you-can-eat access once the beta’s over, or you can opt for nabbing tracks at around $0.99 a pop. Ask real nice-like for an invite to the closed beta here, or hold out for the Android or iPhone version. Oh, and U.S. only, of course.