I may be way off base here, but when I've needed to find distances, I've used How Far Is It? by Indo.com. It may be of particular interest (or not) because the details of their Distance Calculation are given, as well as a freely-available perl program for doing this calculation. At one point in time, the results were then displayed using the Xerox PARC Map Viewer; now it appears they use Google Maps. If nothing else, this post should give you a few ideas for Google search terms...