MBTA Google Maps Mashups

While I’m not the biggest fan of the MBTA, I’m in the market to buy a house, and would like it to be near the train so that there is easy access to the city. Specifically I’m looking for somewhere that is walking distance from the train. Initially I was looking for somewhere near a subway station, but I’ve broadened my search to include houses near commuter rail stations. I get a number of email about houses which are for sale, but the first thing I want to look into is location. How far is this place from the nearest train station. Aside from knowing the area, there doesn’t seem to be any way to find this information.