Facebook Connect Script
Use this Facebook Connect script when you want to let your users to login or do stuff on your site without having to create an account.
How to use it:
Don't forget to download the PHP SDK. Test this script on a PHP page
to see how it works and then try to integrate it in your pages.
This Facebook Connect script will also request permission from the user
to give to your website access to his e-mail address.
You can see that in line 36 is where you get user's data.
Code with Love.