Terrific piece of ingenuity by Chris Lightfoot and Tom Steinberg of mySociety — travel-time maps showing journey times via public transport and shortish taxi rides. Using colours and contour lines they show how long it takes to travel between one particular place and every other place in the area, using public transport. They also show the areas from which no such journey is possible, because the services are not good enough.
The detailed map of Cambridge is very interesting because it shows how some destinations in the neighbourhood are easy to reach by public transport, whereas others (e.g. outlying villages) are effectively cut off.
Link via BoingBoing.