Most Tuesday evenings I hang out at NSCoder Night in SF. The website needs update love, but the credo is the same. NSCoder Night is a once a week opportunity for developers in the Cocoa (iOS/OSX) community to get together to code, ask questions of more experienced developers, and meet people. There are several chapters across the world and people often visit the closest chapter while traveling.
In my experience, the conversations are usually technically insightful, the people are friendly, and theres a sense of camaraderie when someone is working thru a difficult problem.
I'd recommend this event to folks of any experience level; I always leave inspired to work towards being a better software developer.
Tuesdays, 7:30pm at Church St. Cafe in Castro.