FacebookSync introduces a really interesting method of logging in to Facebook web services. Notably they've incorporated a webkit view for handling authentication with Facebook and then pass off the credentials to the underlying app, removing the step of visiting an external browser.

Step 1

Launch app and you're presented with this login window:

Step 2

Once you've logged in, you're told to close the login window. This seems unintuitive, but there must be a listener on the window that, when closed, launches the application that relies on you having logged in:

Step 3

If you've logged in successfully, the app begins syncing with your local address book: