The Facebook API allows third-party web and desktop applications to interact with Facebook features. There is an excellent shared-source library for .NET to wrap the Facebook calls but currently it only supports the full framework. I did some work converting this source to compile and run on .NETCF v2.0. There are some example screens here of the login process, and pulling back information about our book group.
Since the login screen uses the same page as the desktop it’s not a great fit on a Pocket PC screen, so that’s an area for improvement.