You've seen the opening credits and the trailer — now check out the first sequence from Avatar: The Legend of Korra, in which the series' protagonist beats up some goons. We saw a snippet of this scene in the trailer before. Looking jazzy! The show will debut sometime in 2012.
UPDATE: Here are three more scenes, including a boss training sequence. Be forewarned that there are some pretty heavy spoilers coming. Hat tip to Syafiqjabar of Mars!