The government's cash for clunkers program has been so popular that the $1 billion fund set aside to pay for it has nearly dried up. With the chance to take up to $4,500 off the sticker price, buyers have flooded dealerships to trade in gas-guzzlers for new cars with better gas mileage.

So if you didn't make it to the dealer last week, have you missed your chance for the cash—and are you stuck with your clunker?