Similar in spirit to Doodle-O, here are two drawing games, playable by artists of all ages and skill levels:

• The Doodle Association game, where each doodle inspires the next, leading who knows where.
• My Team, Your Team, where two players one-up each other creating characters with powers that beat the last.

And in case you need more inspiration, here's a stop-motion video made on a whiteboard. The whiteboard in my office is not this interesting...