http://browserver.org/ is a pretty simple but spectacular tool. It makes your browser a webserver by reverse proxy(ing) web requests to your (private) IP/DNS location via their server.
The Node.js code is at GitHub jed/browserver-client and jed/browserver-node and this could really make some powerful XSS PoCs (checkout their Location detection).
It also could help with remote support and O2 Script debugging :)