Lots of great ones above. I'll add:
Nonperforming arts groups - music jams, strumalongs, community singing groups, drumming circles, drawing or writing meetups
Courses and workshops - postsecondary, noncredit, community-based, etc
Topic exploration groups - philosopher's cafes, death cafes, psychology discussion groups
Spirit focused groups - meditation circles, "small groups" at churches, chanting groups, small grassroots spirituality groups