Google Developer Group
Google's isn't strictly open-source, but they contribute a lot to the open source community. Freeside Atlanta has a new subgroup for Google Developers that cover topics like polymer.js, html5, etc. Check them out.
Geekspace Gwinnett Moves In
The region's latest makerspace, Geekspace Gwinnett now has a home and is building out. I went to one of their regular Tuesday Open House events last night. They're in the building out phase. So far they have Wifi and workbenches with a couple of older osciliscopes. In the back shop area are a couple of drill presses, an old Craftsman table saw in need of a tune-up, a small metal lathe, cutoff saw and scrollsaw. A milling machine is in the works as soon as moving equipment can be arranged. All in all, about a dozen people showed up and the space has great promise. So come out to one of their events and learn more.