There are several plugins to integrate WordPress into Facebook, one of the best is Wordbook.
This plugin allows you to cross-post your blog posts to your Facebook Wall. Your Facebook “Boxes” tab will show your most recent blog posts. This app is not for blogs hosted at WordPress.com. After activation, the plugin will walk you through adding this Facebook app.
Integrating A WordPress Blog Into Facebook at: http://www.smashingmagazine.com/2009/09/14/how-to-integrate-facebook-with-wordpress/
To intergrate Facebook into WordPress. using Facebook Connect WordPress plug-in.
WordPress plugin that allows direct integration of WordPress blogs with Facebook using Facebook Connect:
Build a community
Login using your Facebook account
Send comments to Facebook profile feed
Invite your friends to the blog community
See last visitors
Facebook share counter
Facebook fan page widget
Facebook comments box
Facebook user email store
Integrating Facebook In A WordPress Blog at: http://www.smashingmagazine.com/2009/09/14/how-to-integrate-facebook-with-wordpress/