1. Find a map you like. I went with one of the Transvaal from the late 19th century, a German map of Lithuania circa 1915 and then a Rand McNally Atlas map of South Africa as it was pre-1902.
2. Diddle it in your program of choice. I printed mine out using MS Paint, as it allowed me to fuck with the % of the page the map would take up, as well as preview how large it would be after printing.
3. Print that motherlicker out and take the scissors to it.
4. Here's where you have options. I wanted mine to look aged, and you can do this a few ways. I did a tea stain/food coloring combo. The box said red, yellow and blue in a 7-2-1 ratio for a light brown, but I'm dubious of that. Don't be a-feared to play around with the numbers, though less red would probably be a good i-dear. I imagine you could also use paint baths (think wash, only with mas agua) to good effect. Whatever your mode, remember this is paper, so don't get rough with it. Don't be reticent to let it dry and then add more color to different spots.
5. ????
6. Profit?
That's how I did it. There's probably plenty of other ways to skin this-here particular cat.
EDIT:
As a post script, it occurs to me that you could just as easily stain your paper before you print your map on it. It would make it less likely you'd wash the ink off it. I'll have to try that out at a later date.