I stumbled across a fantastic site/tool called Odosketch. This is a sketching application driven by Flash that allows you to save your drawings on the site, so others can view them, clone pictures you like of others and modify them, and just generally doodle and draw and have fun. It's a lot more fun with a graphics tablet, but you can have a lot of fun just with the mouse. Might be difficult with a touchpad.
Some of the colour selections draw brushlike strokes that widen with length. Others draw pencil-like lines. There's a white colour tool you can use to paint over your colours and blend them (the background is a pale grey with flecks to make it look like recycled art paper). When you're finished, save your picture and you can watch it redraw itself at high speed. Saving a picture requires a signup, but you just need an email, name, and password to get started.
This is a silly sketch I did, based on a previous sketch of just the cat. I cloned the first sketch and added more colour and background. With the replay you can see all the erasing I did and all the white application that I later worked into a face that was actually visible.
Take a look at both the featured sketches (my favourite is the alien abduction one) and the current sketches, which shows things posted by people in real time.
Odosketch is a great little tool if you feel like arting it up a bit but don't have a lot of time or don't want to get messy. Now if you have an art attack right before an important interview, you can satisfy it without getting paint on your nice clothes.