Lately I've been learning to illustrate in Flash. Here's my first original Flash illustration (that I'm willing to share publically). The SWF is under 10K. That is amazing when you consider a PNG of the same image would be around 60K, a JPEG would set to a quality of 80 (so it would look almost as good as the PNG) would also be around 60K. Even those are not really fair comparissons because the SWF actually has some animation in it and you have the ability to zoom in and view it at a higher resolution.
I started the illustration by doing a pencil and paper sketch. Then, instead of scanning the sketch, I just drew directly in Flash referencing the pencil by eye.
Two resources which have been very helpful in learning Flash's illustration tools have been the book Illustrating with Macromedia Flash Professional 8 and the site CartoonSmart.com.