How to let users register with their Facebook accounts? I would like to let visitors choose between signing up by using Drupal's core sign-up system, or to register using their Facebook account.

I looked at a few Facebook related modules but that was a little confusing, and I couldn't make up my mind on which one to use (I don't use Facebook myself so I guess that doesn't help).

What are the differences between regular registered users and those who signed up using their Facebook account?
Will Drupal have access to their emails?
Drupal for FaceBook is the one you need.

You can configure application settings and which information you want to get from users, such as email address.

Unlike other suggestions, this module does not rely on third party providers and registrations other than Facebook.