The second season of The Legend of Korra can't come soon enough. Fortunately there's some stuff to tide us over, the most recent of which is a cool interactive book Nickelodeon released for free today on iTunes.
It's called The Legend of Korra: Enhanced Experience. There's concept art, storyboards, animatics and more included in said book according to IGN. I'm downloading it right now (and you can too here), but already the storyboard versus final scene stuff looks interesting.