Where to meet other people in "internet start-up mode" in SF?

I’m new to SF (coming from Europe) and just starting up an Internet company, social network, type site. Looking for funding, hiring key people, gearing up for marketing efforts, that sort of thing. Since my main reason for being in SF is not business related but personal, I don’t really know where to start meeting people in the same situation.

It seems like most people (or at least more than anywhere else in the world) are running start-ups or are doing business online so I figure that there must be tons of places, meet-ups, gatherings, bar nights, and what not for like minded people. I just don’t seem to find them.

Am I wrong? Any ideas?