Here's a great link for those of you interested in pitcher and hitter mechanics. There hasn't been a lot research into how much mechanics can predict success, so take it for what it is, but the guy who writes these pieces --Carlos Gomez-- had a very good rate of success when predicting the best draft picks of 2006.
Jeff Albert does another interesting mechanics website. Good stuff for sure.
(Special thanks to ryanhoward06 from the Beckett Message Board for the helpful links)