I haven't been to San Francisco in years, but from what I remember, the most interesting stuff was around these places:
The pier, and everything around it, has some interesting stuff. Depending on where you're coming from, Chinatown might have some new and interesting stuff, too. The Metreon is kinda cool, if you're used to arcades costing a buck a play. There's also a lot of decent places to eat around San Francisco, but I don't know of any in particular off hand.
Don't go to the area known as the "tenderloin," it's really shitty and probably dangerous. That, and Oakland.
There's also the stereotypical tourist attractions like Alcatraz and the Golden Gate Bridge.
Oh, and there's also a small J-Town if you're into Japanese culture, like most 4channers, nothing like the one in Los Angeles, though.
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy
All work and no play makes Jack a dull boy