Let's Chat is a persistent messaging application that runs on Node.js and MongoDB. It's designed to be easily deployable and fits well with small, intimate teams.
A little server that enables public access to a Slack server. Like Freenode, but on Slack.
aaronpk: I just had a crazy idea to create an IRC server emulator that is actually a micropub client and indieweb reader
Hector is a private group chat server for people you trust. It speaks a small subset of the IRC protocol and is written in Ruby with the EventMachine library.