Academy of Sciences has a new Coral Reef exhibit up if you want to check that out, all their stuff is always cool, I'm going to head down there in the next week to check it out myself.
Twin Peaks also has a really nice view of the city, recommend checking that out.
and if you want the best god damn hot dog of your entire life keep an eye out for a Let's Be Frank hot dog cart, there are only two in the city and the easier one to get to is right next to The Warming Hut cafe at the very end of Crissy Field closest to the bridge. Check their scheduele to make sure they're there first. (and seriously dude I don't even like hot dogs but that stuff is legit one of the best thing's I've ever had find it and shove it in your mouth hole)