http://www.cartographersguild.com/showthread.php?t=4676 was done from a back and white mask in Photoshop and Wilbur. The first cut (not shown) was done entirely in Wilbur, but I didn't show it because there is an annoying cardinal direction problem with the distance calculator in Wilbur that causes square artifacts to appear over longish distances.

I will try to remember to write a tutorial for this but I'm a little swamped with coursework and workwork at the moment.