I'd Rather Be Frying Bacon

I fall into both categories, though much more so into the "nerds who really like maps" division. Using the Google maps interface, a guy in Hoboken who was training for a marathon and wanted a relatively simple way to calculate his running distances put together the Gmaps Pedometer. Essentially you doubleclick points along your route and the total distance (along with that of the last segment entered) are tallied on the right side of the screen.

For example, here is a closeup on the route I ran this morning (which turned out to be a total of 3.8 miles):