On the same note that Laserman was hitting, I would start your motion library by having a good hard look at the Muybridge books if you can find them - those are the single most useful resource I've ever seen for studying realistic movment, balance, and the body in motion; I don't think they've been equalled yet. Each volume is fairly pricey, but if you're serious about animating, indespensible. I've never really seen much in the way of truly useful magazines. Most of the really interesting stuff I've ever learned has been through colleagues, or figure drawing and anatomy for the artist classes. The vast majority of mags I've seen cover kind of a general overview, and summary of how something was appraoched, but aren't terrifically helpful for teaching the specifics of anything. The siggraph stuff is very cool if you've already got a grounding in the field, and will defineitly give you some awesome ideas about how to approach a problem.