This is absolutely one of the best site for training your character designing skills.
Basically, the site contains a Flash application that flashes pictures of characters (male/female) in various poses. You get a pencil and paper and draw the characters in those poses.
As part of the training, the pictures will keep rotating every few seconds (which can be adjusted from 10 - 90 seconds - default is 30 seconds). This forces you to train yourself to draw them quickly.
