I do a lot of posting and general fun having on the somethingawful.com forums.
My favorite of the areas in the forums is BYOB. There, a guy can goof off and talk about video games an other random stuff without having to worry about too much unnecessary drama that comes from other forums. There's some fun people there and I like to let them throw ideas at me, it keeps me drawing.
Just before I graduated I started a thread in which I would always reply with a drawing. I didn't promise I would reply to every post, and I didn't say I'd reply to a post with an image that was requested of me. Here's some of my fave doodles from the thread.
The first thread was "goldmined" and can be found here. I started the new thread last night.