This is a free little thingamy called Groupboard. It has games, realtime chat, and a whiteboard you can doodle stuff on. It's free and doesn't cost anything, though there's a banner ad and a popup ad because of it. It features:
Have fun with it. It's quite compatible and (I think) doesn't need any plugins. If you have problems getting started, don't close the popup ad until the board has loaded. Of course, there's always the (slim) possibility that there's already 5 people using it.
Standard rules apply. Basically; be nice. And don't draw anything you wouldn't show to your mother.