We recently used the parking at the Clarion hotel
http://www.quikparksfo.com/
$10/day (plus 10% tax). Very quick to/from the airport. Plus, every three stays gets a free day. We compared to ParkSFO, and it is just about always cheaper at the Clarion, excepting the 2-day coupon. With the 1 day (and a 3 day minimum), ParkSFO is cheaper unless you're a few hours over (like we were
) and then Clarion wins.
Cheers.
The couple of times I parked there, I was not impressed with the shuttle frequency compared to ParkSFO. I did a lot of waiting.