While the government's program to get less fuel efficient cars off the road ultimately fell victim to its own success, drivers in Portland, Oregon who didn't get in on the deal now have the option of really reducing their emissions: by trading in four wheels for two (see Entrepreneur Rides Bikes for Clunkers).
Joe Bike in southeast Portland offers two options for getting inefficient vehicles off the road (and has expanded the definition of a "clunker" to include bikes in a state of disrepair):
A driver who donates his car (in any condition) to the American Lung Association can bring the receipt to Joe Bike in exchange for a ten percent discount on a new bike, plus a lifetime membership with Zipcar.
A cyclist who brings in her slightly-worse-for-wear (but repairable) bike will get $50 to a hundred dollars off a new one, and the old bike will be fixed up and donated to the local Community Cycling Center.
For more, check out Joe Bike.