I always use Dante to drive me to and from the airport. He's a nice guy, he speaks English and he's reliable (his car is only so-so though). Don't give his name out to too many friends because he tends to be booked -- I always email him a month in advance to be sure. His price has crept up to $30, but I suspect that's still cheaper than most options.

http://dantesairporttransfers.hazedaze.com/