Hivemind
Turntable.fm authenticated communication server
Hivemind is a node.js server that accepts web connections, sends them an unnecessarily randomized key, and then expected them to send that key to a bot sitting in a private room. If they do, then they can talk to other users by userid or broadcast to the room they're in.
Why is this significant?
Because they need to private message the bot, the server can confirm that they are definitely logged in from that client. This means that this system can be trusted to ensure that any message sent can only possibly be received by the intended user(s).
Neat!
-chrisinajar