The rationalist community has chapters all over the world, the oldest being the NYC community, which has been around since 2009. Many of these groups are centered around regular meetups, or call themselves 'meetups'.
These are posts about meetups and local communities in general, not about specific communities (unless they also provide general insight).
For example - What are meetups actually trying to accomplish?
For specific meetups see Events(community)
See also - Community