I found this interesting flash-based drawing tool online a few months ago, and I had completely forgotten about it until I was browsing through my images and found a few screen captures of the drawings I'd done with it.
It's called
The Scribbler. At first, you use the mouse to draw something-- anything-- with basic lines, and when finished, you click the "Done Drawing" button, and the engine re-draws your image with random "scribbles." You can control the scribbling line width, color, etc (using set or random values), and create some nifty effects. There's a large gallery on the site, with some cool stuff in it.
Here's a few samples of what I did with it awhile back, I'll probably fart around with it later today and see what I can come up with:
