I'm driving from to . How much further is it if I stop at on the way?
This turned out to be pretty trivial, using the Google Maps API. (Especially since Google Maps will interpret such a wide variety of format! You can specify a complete address for maximum accuracy, a street alone, a zip code, a city, a state... even a country!) The only hard part was that the documentation wasn't very clear on the necessity of attaching a "load" listener to get the distance object.