Here's a before and after of something that I put together with the photochop webappy thing that I put together. This one was created by reducing the colors of the image, blurring the result and applying the drawingify filter.
The drawingify filter takes the original image, blurs it, averages the result with the original image, then applies the photocopy filter and blurs that result. This generally gives a fairly convincing pencil-drawing style effect.
Seeing as this is mainly a test of HTML5's canvas element, it'll die a fiery death on internet explorer, but should work happily on most modern browsers. Savepoint averaging only works on Firefox 3.5 due to some awkward security settings on other implementations.