I say 'day 0' because the summit doesn't actually begin until tomorrow (Monday).
A bunch of us in town already met up at the Googleplex this afternoon, just to hang out and relax. We found an empty conference room with 2 projectors, whiteboard, and sofa. After some socialization, we decided it would be cool to try and get Subversion 1.4.1 finished ASAP, so that it makes it into Debian Etch (whose deadline is the week.) So we hooked up two of our notebook computers to the projectors, and spend a couple of hours doing group code reviews of the 1.4.1 STATUS file, examining diffs, and dropping votes into the file. We didn't quite finish, but it was still quite a bit of fun.
Tonight, 13 (of 30) of us congregated at Yuet Lee, kfogel's favorite Chinese restaurant in downtown San Francisco. Afterwards we retired to kfogel's apartment, where we spent an hour or two debating the merits of distributed version control systems. I'm sure we'll have to repeat the debate tomorrow, when the summit really begins and the other 17 people show up!