Find a [whatever] near you with Rails and the Google Map

Has anyone built a "Find a Physician" or "Find a Dealer" or whatever using Rails and the Google Maps api? I've found a large number of tutorials ca. 1996/7 and one seemingly current project on Github for a general-purpose Google Maps connector gem, but I'm hoping to find some tips about using the map to find the nearest physician's practice to the customer's Zip code. There would be a few hundred practice locations, all in upstate NY, if that makes any difference.

I'm very familiar with doing this in the traditional Great Circle calculation, but I was interested in learning a new trick -- how to do this with the Google Map -- seeing as that might be more accurate in a sparsely populated area.

Thanks in advance,