Hit up the Academy of Sciences while you are here. It's in Golden Gate Park (lots of other neat stuff in the park, Botanical Gardens, DeYoung Art Museum, Japanese Tea Garden, etc. (and, you can drink in the park, if that's your thing...)), and has some pretty cool exhibits/displays.
Depending on how much time you have, and what your transport options are, it might be worth hitting up some other spots in the general bay area.
Aqua Forest, while not my favorite store, is definitely worth dropping by, especially if you'll be in Japan town anyways. I'm personally fond of Albany Aquarium - it's over in the East Bay, reasonably close to the El Cerrito Bart stop. Not as impressive looking tanks as some of those in Aqua Forest, but most of the staff strikes me as friendlier, if not more knowledgeable, and the livestock and plants they have generally look really good.
Chinatown is always worth visiting, especially if you are partial to the food or anything.
And I'd second hiking up to Coit tower- you might get to see the parrots (and if not, you'll likely hear them...)
Golden Gate Bridge is worth visiting if you are at all interested, and there are also a handful of old bunkers/gun emplacements scattered around the hills near there if you feel like exploring. Last I checked, most were either bolted/welded up shut, and the parts that weren't were, well, full of NSFW type debris...