Justin Bieber second top on Billboard's "21 Under 21" list

Whose tunes will be filling the Top 40 during the coming year? If Billboard is right, it'll be a bunch of pretty young things. The magazine just released their "21 Under 21: Music's Hottest Minors," list, and it's a mishmash of radio staples (Sean Kingston), fresh faces (Willow Smith) and a few we've never even heard of (Never Shout Never).

Country sweetheart Taylor Swift, 20, took the top