Update (11/26/2013): I'm updating my recommendation. Since a sufficient amount of time has passed since I wrote this answer, I would recommend python-social-auth or django-allauth as the best tools for the job. They are active projects with good documentation and support for a lot more than just Facebook. I've had success using both.
I have had the most luck with adapting django-socialregistration with django-registration (0.8). Since you're working with django-registration, you're going to have to do a little bit of work, since all three of those packages assume the role of both the creation and the authentication of the user.
I was just going to explain what needed to be done, but you inspired me to finally get my version out: hello-social-registration.
Like I alluded to, it separates gives the registration functions to a django-registration backend and handles all the authorization itself. I've been using this on my near-beta application for a while now with no problems (I also handed it to a friend to use a few months ago and he got it to work without much modification).
It's definitely not ready to be a plug-and-play reusable application, yet, but hopefully it'll provide you with some insight. :)