For four years now I've wondered where to buy computer stuff in San Francisco. Previously, I would just order online or wait until a fortuitous trip to Palo Alto enabled me to go to Fry's Electronics (a place I love to hate). But from now on, I'm going to go to Central Computer. I bought some stuff there the other day, and the place was full of shiny computer parts, many of which had little lights on them (irresistable!).
Central Computer: it's at 837 Howard Street, a couple doors down from Buca di Beppo.