So, I’ve been playing around a bit with MonoTouch and Facebook’s Graph API.  It’s a nice, JSON based API, pretty simple to use, and quite powerful!  Anyways, I decided to build a little View Controller to handle the actual authentication.  Facebook uses OAuth 2.0 which basically consists of you showing the user a facebook login page, where they login and then accept the permissions you are requesting on their behalf.  Once this is done you get an access token that you have to send Facebook for any API calls for that user.  From a user perspective, this works nice since third party apps never see their username and password.

So, I’ve posted a Gist on GitHub with the simple controller, using a nice Activity indicator and overlay:

Cheers!