My first experience was at an eating club in college. (Think: a coed frat, except you eat your meals there, and the environment is a bit less rowdy.) This was literally like a gentlemen's club and had actually been modeled on them in the 19th century. My club was even more 19th century than most, being self-consciously old-fashioned. We had what I consider the basic requirements: cameraderie with admirable people, a space of our own, frequent meetings, and alcohol. And the remarkable thing: it worked exactly as it was intended. It was a good influence on the members: shy people came out of their shells and rowdy people became more responsible. A lot of people got jobs through club connections. A lot of people got dates through the club. A lot of us learned enormous amounts about each other's areas of expertise. And there was a sense of loyalty and even honor connected to belonging to the club.

Now I'm in a regular LW/OB meetup group in New York, which in a very different way serves the same function. It's as self-consciously futurist as my eating club was self-consciously historical. And instead of college students it's mainly young professionals. But it has the same basics: cameraderie with admirable people, regular meetings (if you live close by), some plans for a permanent space of our own, and sometimes alcohol. And it has some of the same positive effects. Useful professional connections; sometimes romantic connections; learning a lot from other people's areas of expertise; a focus on self-improvement; and a sense of loyalty to each other. We are becoming more awesome together.

The other group that might half-qualify as this sort of a community is Chabad, which I've attended occasionally. I've seen it have the same density of impressive people, the same almost loving loyalty, and even professional connections (like recommending a lawyer). Obviously that's a religious group and so not what we're looking for here; but if a religious group reminds me vaguely of the community-building strengths of the secular groups I've actually belonged to, I'd say that's a sign that the secular groups are doing something right.