California's Cash for Clunkers program is accepting new applications. You can get up to $1,500 for your old vehicle if it meets program standards (click here for details).
Applications take six to eight weeks to process, so you should get your online application in right away.
If you need the money sooner or your car doesn't meet the program eligibility requirements (it must be a model 1998 or newer vehicle, currently registered in California, have failed its most recent smog test and be driveable to a local dismantler), there are local air district programs that might be able to help.
And, if you meet a certain low income standard, you might be able to take advantage of California's Cash for Clunkers program even if your car has passed a smog test.
An estimated 700,000 high-polluting vehicles were taken off the roads ten years ago in a nationwide Cash for Clunkers program. Unlike that one, you do not need to put the cash toward a newer, cleaner vehicle. The current California program is a straightforward swap---your car gets scrapped and you get the cash.