Ircd.js: A Node.js IRC Daemon
github.com
github.com
Coolest application I've seen come out of node.js is http://mrdoob.com/125/Multiuser_Sketchpad_HTML5. I'd be interested in what others are doing in it; let alone, how they got about doing they wanted to do in it.
stephank's orona (html5 tank game) is a neat project: http://github.com/stephank/orona
I would particularly recommend checking out socket.io, and maybe some of the projects using it. It's a way of doing realtime browser-server communication, which uses websockets if the browser supports it, and a variety of increasingly ugly fallbacks on browsers that are old and/or made by Microsoft. You can make some very cool stuff with it.
Also, definitely get npm, the node package manager. It makes installing libraries much easier:
Now, what would be really interesting is if you were to add a WebSocket layer into the server, so one could write a browser-based client that would directly interface with the IRC server without having to proxy like mibbit does.
I made a web-based chat system maybe a year ago called JsChat, so I might use some of the stuff I learned there and do a nice Socket.IO thing.
It's not IRC per se but it's a simple enough example of realtime chat via socket.io.