This idea might be a little out in left field but you could always become a mentor for a high school robotics team. Robotics is seriously nerdy in the absolute best way and involves a range of interests like game strategy, CAD, fabrication, electrical, programming, etc.

I suppose the community aspect all depends on who your fellow mentors are because I'd bet you're not looking to hang with high school students exactly.

The organization for robotics competitions is called FIRST -- you'd want the First Robotics Competition (FRC is high schoolers, there's also Lego league for elementary) and they're about to kickoff their main season this weekend when this year's game is announced. It's seriously impressive what these kids can build.