Facebook made an announcement of a a new JavaScript client library that allows a Facebook application to be accessible on any website.
The library does not require any server-side code on your server, so you can create a Facebook application on any web site that serves static HTML. The application lives within within an iFrame and makes Facebook API calls.
Facebook Developer Blog: "JavaScript Client Library for Facebook API"
TechCrunch posts: "Facebook Apps On Any Website: Clever Move"