Very nice style. Crisp, attractive, and a nice amount of detail. I also love the type of textures you use in your maps.
Do you hand draw the roof textures for every single building type you make?
For us dumb folks, it would be great to see this made into a detailed step by step tutorial (such as one for GIMP).
I hand draw all the roof stuff. I made a tutorial for how I do my town maps which you can find on the tutorial forum. I can't remember the exact link but it is just called "town map tutorial" and obviously the thread author is me so it should be pretty easy to find. It is for photoshop though not GIMP but someone in the thread managed to apply most of it to GIMP.