Meetup works really well in my city. Recently a few friends started a meetup group for a taco night with other folks in the tech scene- no speakers, no frameworks, just some people getting together after work. Some of the group that set up the event came, but because it was on meetup, several total strangers joined us and we all got to hang out and shoot the breeze. Several of the people who showed up were people working remote jobs who don’t have an after work socializing option when they want one.

Thanks one example, but shows the overall idea: anybody going to a meetup event has already accepted that this a publicly known event where there will probably be some new people, and wants to socialize with new people too.