Mapnificent is a Google maps interface that plots the areas of a city that are accessible by biking, walking, and public transit within the point of reference you select.
It visually frames the city in a more relevant way for sustainable development. Instead of merely *hoping* that people ditch their cars for bikes and public transit, this could be a tool to assess potential alternatives just by entering your address, not unlike the site Walkscore already famous in the real estate industry.
Here's a couple cool examples from right here in the busiest neighborhoods of Seattle.
Via: Seattle Transit Blog