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.
Launch app and you're presented with this login window:
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:
If you've logged in successfully, the app begins syncing with your local address book: