what's going on, on a Saturday night?

I'm such a homebody. My brother Andrew is visiting me, though. He's here for a week. I don't work many hours, so we'll have plenty of time for SF sightseeing, and we both want to do a Muir Woods and Stinson Beach day. I was just thinking, since it's Saturday, we should take advantage of stuff that might be going on.
Anybody know of fun stuff to do tonight? If you friends are also at loose ends, I'd love to get together to hang out with buddies, if it's close- like Concord, or Berkely/Oakland, and not too gaming-focused (my bro's not a gamer, though I hope to make him play Settlers of Catan with me. Damn! Ryan's on a mission, or we could play right now!)
If we don't find something wicked cool to do tonight, I think we'll just settle for a "Ryan & Stacey make a night of it in Fairfield" type evening- that's the movies, Barnes & Noble, and a chain restaurant :)
Andrew is a totally low-maintenance guest, though! He's good fun, and we have fun just being goofy like Dunkleys do.
He's only 17. I can't take him to DG on Monday, can I? That's an over 21 place, right?
Stacey