Near the Moscone Center:
One of my favorite places. Great coffee to get your energy back after a long talk about rigging (try the New Orleans iced coffee for a real kick). If you get there in the morning, grab one of the croissants fresh out of the oven. The staff are great, and could probably give you a bunch of pointers on good places to check out in the area.
Elite Audio and Coffee Bar
Because what goes better together than coffee and high end audio systems? Sure. Anyway, this one is very close to the Moscone, but will probably be packed full of people, so keep that in mind. Cappuccinos here are great, and once again staffed by a good crew of people. They serve Neighbor Bakehouse pastries most days, and those alone are worth checking out.
Great coffee, and also a good opportunity to take home a San Francisco local roast. A little bit of a walk from the Moscone, and there will probably be a line either way, but well worth the walk. Once again, Neighbor Bakehouse pastries. Eat them!
Continuing the trend of a store that sells something (in this case high end cycling gear) but also serves a decent roast, Chrome Industries is a short walk from the Moscone down 4th st. It's also near the Hotel Utah, which serves a different type of brew (worth checking out for beers!).
Not so near the Moscone Center:
Contraband Coffee barIf you find yourself for some reason near the Polk street area, Contraband Coffee is nearby on Larkin and California. It's got good coffee and hot chocolate. The snacks are good too, but it's worth checking out Flower and Co. nearby or MyMy for a real meal. I have seen Neighbor Bakehouse pastries here too. See a trend?
If you find yourself near Fort Mason, the interval is a good place to stop by. Good coffee, provided there aren't too many people around. The crowd can occasionally be a bit of a downer.
Four Barrel CoffeeIf you find yourself in the mission, check out the four barrel coffee place down there. I've heard mixed opinions about the Four Barrel coffee, but I'm a fan. Delicious! Being on Valencia St, its also surrounded by a bunch of excellent places to go grab lunch or dinner.
The Mill serves four barrel coffee, as well as that whole thick toast thing. The toast is good I guess, but I really go there for the coffee- that's really good. They sell bread too which is pretty damn good bread, although carrying that around the conference floor might not work out so well.
So that's some places to get you started- have you found any that you think should be on this list? Also, hit me up you you want to meet up for coffee and talk game dev stuff. As you can tell, I like coffee.