check out these for non club ideas:
funcheap.com (loads of free or cheap things to do. only in SF)
citylights.com (legendary beat writers bookstore)
yelp.com (check out SF cuisine)
aquariumofthebay.org (rad)
go check out twin peaks during the day. it is amazing. just at the top of Market.
go see the seals. it's more fun than you might think.
take juandingo's suggestion and hang at Market & Castro on a saturday night. more entertainment than you ever wanted.
(i can recommend an excellent mexican place if you get hungry)
if you like garlic, hit Gordon Biersch brewery by the water. yum. can't remember what they call it, but some vodka drink with rot beer and some other crap. delish.
enjoy.
dc