Meetup.com may have a name that suggests it's another one of those online dating sites - but that's not at all true.
Here, you enter a national site by finding your community within its database. Once there, you can roam thru the topics, or scan the current month's calendar, for things to do -- and see the members of the various groups who are coordinating getting together via the site.
Walkers and runners can find events here, as well as info on trails and upcoming races. Dog lovers can find out about dog parks and dog walks. Farmer's market info is here, and so is lots of stuff on a wide variety of support groups.
It's free to join. There is a fee to start a group.