Online Communities - Where Should I Be?

So one of my goals developing Lab Rats is to make it available to as many people as possible. So far, all of my attention has either been here, or over on the Legend of Krystal forums. The internet is a big place though, and I'm sure there are a ton of communities that I don't even know exist.

So, my question to everyone: What are some communities I should be aware of? Where do you frequent on a regular basis?