My brother just created a really cool online sketching site called Sketch Monster
Sketch Monster is a place for all different skill-levels of drawers, sketchers, and illustrators to show their work, learn, and be inspired. To participate, simply create an image for the current subject. Its simple, its free, and you don’t have to sign up for anything!
The subject of the sketch changes every 10 days or so. The current topic is ‘monster sketches.’