I don't organize our local group, but I participate.
It's organized through meetup, but originally it was a mailing list. I found it through the poly events all over link that redpepper has in her sig line. It's also a huge, secret facebook group. The meetup is a once a month meeting a local coffeehouse, they have a room off the main place. We all get a drink and some get a snack, and the room is free. The first hour is a discussion. Sometime they pick a topic; the last time they had cards so peeps could write questions, and the questions get read and anyone with input can speak. Then they break for drink refresh, potty breaks, and coming back is just informal discussion amongst anyone in the room. It's nice for those who are shy, they can just be in the room and hear discussion without being put on the spot; then if they like, they can talk one-on-one to folks in the social time. Those who dislike formal discussions can come late, or politely wait for social time. Frequently there are lots of kids on laps or underfoot. This last time there were no kids, but that was the first meet I'd been to with no kids.
There are some passionate gamers, and they've organized a once a month poly game night, which is just like any other game night, but poly peeps show up for that.
There's a core group, but every meet always has noobs. Sometimes they keep showing up (like me).