I keep coming across mentions of node.js, but wasn't sure what it was. This morning I've been watching some tutorials and reading up a little, and from what I understand it's basically a network server framework built on top of Google's V8 JavaScript engine, really an abstraction for socket programming. It's main advantage is speed and scalability, due to it being based on an event driven I/O model, rather than threaded, like most other languages or frameworks.
This video from node's creator, Ryan Dahl is a pretty funny and very informative introductory video. I'd recommend programming along with watching it:
Here's some further links:
http://nodejs.org/docs/v0.4.8/api/synopsis.html
http://howtonode.org/
This podcast is also a good source of information:
http://herdingcode.com/?p=299