As a metropolitan Washington, DC resident, I'm aware of lots of cool transit initiatives ranging from public transit to car share services to slugging . . . but I just heard of a super-cool inititative in Arlington (one of the close-in counties). It's called the car-free diet.
The car-free diet teaches people the advantages of going car-free, and gives advice on how to do it. The website includes a calculator, that with a few quick inputs, shows you much money you'll save, how many calories you'll burn and the amount of CO2 emissions you'll reduce with your choices. It also links to information on transit options (both man-powered and machine), suggestions of places within the county where it's easy to go car-free, and tons of links to other resources.
The car-free diet even has its own blog: http://commuter.typepad.com/the_carfree_diet/ - full of great advice for those looking to go car-free and personal experiences of those who are trying it. This is a great initiative for a county where there are lots of people, lots of transit, and lots of interest in environmental friendliness.
As my daily commute takes me through parts of Arlington, I'm definitely going to take advantage of the information about this diet.