When you ask questions like this, you really need to state where exactly you live. If you don't, all answers are going to be vague generalities since we can't say "Stop by your local Founder's Exchange". However, if you said, "I'm in Pittsburgh and looking to meet a cool and smart co-founder," then I know a dozen different places to meet people, and there's probably a bunch of people on HN from your town too who might grab a beer and introduce you to people.