David Kellogg released one of the most amazing Firefox plugins : Plain Old Webserver (POW), which adds a server to your browser.

Yes. You can run your own webserver within the browser. Although I didn’t get past the "Hello World" application, it’s amazing that this nifty tool supports Server-side JS, GET, POST, uploads, Cookies, SQLite and AJAX.

This plugin is definitely a must have tool for any web security assessment Thanks to pdp (architect) for pointing out this tool!