The Walk Score uses information gathered from the Internet to determine how easy it would be to live a "car lite" life from that location. The criteria includes the distance from a house to a variety of amenities including stores, schools, movie theaters, etc. Obviously, the more amenities closer than 1 mile, the better the score. In fact, amenities closer than 0.25 mile are even better.
The score ranges from 0 to 100 with 0 meaning the neighborhood is car dependent, 100 is a walker's paradise.
Though it was pretty cool to see how houses for sale are ranked, I was even more excited to see that my house scored a 72! Though I was not concerned about walkability when we moved here 22 years ago, it was nice to see that it wasn't such a bad decision. (I had a feeling it would be higher than average since I walk so often.) I would really like it if it were even higher, but not knowing I would eventually like walking, we did pretty well.
So, if you are interested in buying a house, or just checking out the walkability score of your current home, go to the Walk Score web site at http://www.walkscore.com/.