Looks to be one of the larger WordPress meetup around town. Meetup claims they have 1,100+ members. See their Meetup Page. They're meeting at IgniteHQ on Waddell St. in Marietta. Their description on Meetup is somewhat generic:

We're a group of local WordPress users who get together to share our knowledge and experience, and to meet other WordPress users in the area. This WordPress Meetup is open to all who are eager to learn more about WordPress --- the software, the community, and the business!

They seem to have a good mix of technical and non-technical programs.

Events - WordPress Cobb (Metro Atlanta) Users Group

Events - WordPress Cobb (Metro Atlanta) Users Group