Cool Site to Check "Walkability" of Addresses

Now that we've had a 3rd child, the townhouse we're currently renting is getting a bit cramped. Also, the dip in home prices is making buying our own place a more attainable goal than it was a few years ago. So I was checking out the real estate section on SFGate.com to see what they had listed. I noticed the listings included a "walkability" score. Our current home is rated "somewhat walkable" with a score of 58 out of 100.

I love the concept, though I would quibble over the details of the algorithm. The biggest flaw IMHO is that it's missing one of the most important places to which I would ideally like to walk: church. When DH was in grad school and we lived in student housing we used to walk to church every Sunday. Unfortunately, our current parish is 2.6 mi away from our home, which is farther than I care to walk with the kids on a regular basis. I couldn't care less whether there's a bar within walking distance (one of the categories that *IS* listed) but it would be very nice not to have to drive to Mass every week.