alt Hacker NewsA club I'm active with posts everything to Meetup and Facebook. Meetup is the "official" source of truth for posting events and photos and limited chats related to the events themselves ("Where are we parking?" type questions). Facebook for social chat and announcing "unofficial" hangouts/parties.
Meetup is often used in the groups I'm in. A friend used to organize and it cost the organizers money but no the members. It was pretty ad free.
Now they're asking members to sign up (and pay) for more feature (meetup plus). and show ads. But still decent for organizing meetings.