RPG map-making on the fly and on the cheap

I made this map for an upcoming RPG session.  I like how it came out - I'm no artist, but I was able to use some terrain generation stuff in the GIMP graphics software to do a bunch of it.  I used a shaded version of actual terrain as an overlay for the mountainous bits, and I think it looks OK, even though it doesn't exactly match the outline of the island.

Anyway, pretty good for a few hours' work.  I may post a how-to later if anyone's interested.