This application brings together the many compelling platform capabilities of Silverlight 4 into a rich out-of-browser application in the familiar context of Facebook.
Enjoy the photos, feeds, events, friends’ walls, and inbox mail from your Facebook account in an appealing and user-friendly environment.
Note: Silverlight Client for Facebook is a Silverlight 4 developer preview application. When Silverlight 4 is finally released you may be required to uninstall and re-install the plugin.
Check it out here: http://www.silverlight.net/content/samples/apps/facebookclient/