Late last year, we at Stamen produced a series of interactive travel time maps for MySociety in the UK.
Tom Carden created a Flash-based viewer that let you interactively manipulate your maximum commute time on London's transit network to determine where you should live.
I've been interested in extending that work in two directions: first, the maps produced with MsySociety are valid only for single locations in London, and second, it was necessary to scrape the Transport For London website to get data to work with. Here in the Bay Area, 511.org publishes complete schedules for all public transit in the nine-county Bay Area in a usable data format.
With a copy of the 511.org Transit Data Feed, publicly-available census shapefiles, a modified version of Dijkstra's algorithm, and the magic of Modest Maps' Python implementation, it was possible to create complete travel time maps for all ~1,400 census tracts in the Bay Area. Searching for an address or clicking the map will show area-wide public transit commute times for a 9:00am arrival at the selected location. The interactive slider helps you understand what your housing options are for a given commute.
Not all locations in the Bay Area are reasonably accessible via public transit, but the core urban areas are all well-covered.