"Walkability" is one of the major buzzwords in contemporary urban planning. The idea is simple and makes worlds of sense: living in a neighborhood where you can walk everywhere instead of driving greatly reduces your eco-footprint, encourages a more healthy, active lifestyle, and increases neighborhood safety. It's a buzzword that actually deserves the buzz.
I've always thought that the creation of a system for mapping walkability would be a watershed moment for the urbanist movement. Walkability maps of major cities, provided in some sort of interactive format (read: a website) would not only make choosing a neighborhood easier for homebuyers and renters, but it would serve as a great informal guide for tourists--especially at a time when tourists are becoming less interested in traditional attractions. Knowing where high-traffic pedestrian areas are would be an easy way of figuring out which neighborhoods would provide the best opportunities to explore the local culture.
I found my first walkability map yesterday (there may be more of these out there...let me know if you come across any.) The Sightline Institute, a Seattle-based sustainability think tank, has developed a map of King County's walkable neighborhoods. The color-coded system is easy to understand, though it's not at all interactive and only major highways (oddly enough) are shown as far as roadways are concerned. I also couldn't find any information about how this map was developed (i.e. what factors were included in determining walkability.) Things like living essentials (grocery stores, laundromats, convenience stores), mass transit access, crime, and density are all important factors, I'd imagine. It'd just be nice to see some sort of breakdown. Still, it's a start.
Map of Walkable King County