Pow is a Node.js app written in CoffeeScript. It includes an HTTP and a DNS server and runs Rack apps by way of Josh Peek's Nack library: https://github.com/josh/nack
Run, don't walk, to read through the source... Sam's documentation is really enlightening, for folks who want to try their hand at building little servers in Node.
The screencast shows how it works and why we made it: http://get.pow.cx/media/screencast.mov
If you're interested, you can read the annotated source code, written in literate style and generated with the wonderful Docco: http://pow.cx/docs/