We hang out on IRC
If you want to find some people to chat with about c5 RIGHT NOW, you can jump in the chat room for concrete5.
We're on FreeNode (/server irc.freenode.net in your favorite IRC client)
We're in #concrete5 (/join #concrete5 once you've connected to a server)
Here's some IRC clients if you don't already have one:
PC -
Mac -
Nix -