I organize lunch every week on Thursdays at Eastern Accents in downtown Ann Arbor. About 400 people get some kind of invitation, and attendance varies from 6 to 25+. (One week we filled the restaurant, which was just a little bit scary.)
This week's crowd was good - I counted 18 seats - and the question of the week was asking people to talk about the job they had in college. The answers ranged from selling pots and pans door to door to selling ice cream in Manhattan to running a student bus company to programming PDP-8 computers. One person was there who was in college now and he talked about his startup that connects bands with bars.
The technology of the week was the notice that the Michigan Terminal System has been made to work on the ultra-small Raspberry Pi system. A photo shows the setup.
Organizing an event that happens every week is easy, especially when the venue is open. All you have to do is show up every single week, invite anyone you can find, and make sure that if someone arrives twice that you remember their name. It helps if you happen to be part of a community where people have learned to communicate online for a long time, and where the online community and the in-person community dovetail nicely.