I just picked up Steven E. Gordon's new sketchbook, "Expressions & Attitudes," Volume 2. If you don't know who Steven is, he's the character designer for X-Men Evolution. And when I say character designer, I mean he designed every single character, from mains to background. He was also a director for the series. He also did character designs and directed "Ultimate Avengers," the animated adaptation of "The Ultimates." His designs are simple along the lines of an Alex Toth, but his proportions are more superheroic, with much longer limbs. His sketchbooks don't just have character design sheets, they have sketch after sketch of the characters in various moods and at various angles. It's really a nice package.
His website has a number of cool features, too. He has "How to Draw" sections for the X-Men Evolution characters, including hand theory, one of my weak points. His theories on animated design are a lot like others I have seen (draw straight lines opposing curves, for example) but it's good to have it all in one place. If you ask me, I think he should be putting out a book on how to draw for animation. He has more useful stuff on his website for free than many of the books I've paid for.