Palo Alto Gas - August 4 - $4.63
I used to live in Palo Alto for about twelve years before I moved to San Francisco last year. I go to Paly often for business and to see friends, and every time I'm down there, I seen to end up at the Shell Station on the corner of Lytton Avenue and Alma Street, right across from the CalTrain station. One August 4, 2008, I took this picture of the gas price sign on the corner of the station's property:

The cheapest gas I've seen has been in Davis at $4.17 for premium.