Plugin to organize local meetings among readers

Hi all, which plugin or other means could I use to efficiently let readers organize by themselves meetings in respective countries/counties/towns to watch together a public event very important for the target of my site? I can imagine putting up a forum where people can start a thread for every location, but I wonder if there is a specialized tool. I don’t think to a complex invitational system like mailchimp, but something readers can easily manage and develop approaching the event date, and possibly stay in the orbit of my site. Thanks.