Greyhawk Grognard has posted this article about another article on another blog about maps. The original article can be found here.The blog can be found here (Making Maps: DIY Cartography). It is really amazing the range of uses for maps that it shows.
And GG is right, the article he cites has a lot of applications to gaming, but also so does the whole site. I think I might track down that book that he mentioned if possible. Why am I just restating what he put here you ask? The Hydra's Grotto is a blog, but it is also an idea library and workspace. Also I have a huge love of cartography. In fact on numerous occasions I have paraphrased Dennis Leary when I have said "D&D doesn't lead to devil worship! It leads to cartography!" Indeed, people* comment on my ability to draw really coherent maps when I draw them for non-gaming use. I do not think I would have this skill (among others) if I did not play D&D.
*mainly my wife, but some others too.