The SuperShuttle is a chain transportation business that operates in all the major airports. They advertise door-to-door service...either taking you from the airport to your exact address dropoff point or picking you up at your residence and taking you to the airport.
Some people swear by them, and then, I've heard some horror stories. The last one I took was SFO last week. It was good. Waited less than 5 minutes to board, and was downtown and unpacking in less than 35 minutes. You need to have your zip code ready when you call for a reservation on the 800 number. I didn't, called an alternative van service, and got terribly car-sick.
"Bestfares" always has discounts for them.