I recently found an awesome blog post by Daniel Baulig showing how to link a Node.js server to a libary called Socket.io. Linking the two libraries to the same session ID allows you to now send dynamic messages to the client using a socket FROM your server. Normally with no configuration these two libraries run independently and cannot be called from within one another.
I'm still not sure what I want to do for my game but I'm leaning towards some sort of MMO turned based strategy game. Maybe one where it queries popular open source websites for your user name and gives your character bonuses based on your open source contributions.
Here's some other good Node.js references: