2D Animation

I''m thinking of making a 2D side-on game as my first "serious" game. The way I plan to do the characters is with separate polygons for head, upper toso, lower arm, etc etc. After a bit of a search, I havent really found any good tutorials on how to do this. Anyone have any pointers on where to start, or know any tutorials? I will probably use openGl. I want to know how to store animation "patterns" (such as walking), and how to join limbs together etc. Thanks