DIY Line Design with Shading that Mr. E teaches his 4th graders. I for one have tried this and there are examples on flickr. This is definitely not just for 4th graders! I hate to admit it, but I had to look carefully at some of the flickr designs to understand it (I know, smarter than a 4th grader? May be not!). Check out his tutorial at Art With Mr. E here and more examples on Flickr here. Upper Right Photo: Seuss Worms by scholz at Flickr here, Bottom Left Photo: chaos sampler ATC by scholz here.
I’ve done this since I saw this tutorial and it is so much fun!