No 2. Janrain Engage

This plugin allows your visitors to register and login to your site via external accounts such as from facebook. It also allows the visitors to post and display their activities and comments on your blog on facebook and other social networking sites.

Go here to download.

No 1. FT-Facepress II

This customizable plugin allows you to publish your latest blog entries onto your facebook wall automatically. Other than that, it can publish your content to your facebook fan page as well. It can publish the title, URL and/or excerpt of your post.

Go here to download.