I used to park at the Millbrae BART station ($6/day, plus BART charges & fees), but because of my personal boycott of BART-to-the-airport due to their tripling the airport surcharge, that is no longer an option for me.
Instead I use Burlingame Airport Parking (attached to the Hilton). They usually run about $7.50/day or $45/week with an advance reservation.
For my most recent trip, departing Christmas Day, they were already full. Fortunately I found a park-and-fly rate at the Crowne Plaza for $89 all-in, including 14 days' parking. Obviously not good for MRs, but for longer stays (mine is 14 days exactly), it's quite a deal. And you get a hotel room (and IC stay/night credit) thrown in, too.
