Too late nw, but for what it's worth:
Buzz 9 is great - a tiny retsaurnt/bar in SOMA. I agree with LV re: the Metreon. Check out the Where the Wild Things Are store upstairs
The San Francisco Museum of Modern Art is great. Very central too. Great cafe for afterwards.
Take the cable cars. I'm not that fond of Fishermans Wharf, but I love taking the cable cars there.
Wander through Chinatown. Always interesting.
The Palace of the Legion of Honour is worth a look (great views from up there too).
So much more...I can't believe it's already 3 months since I was there
