Facebook allows you to quickly and easily import an external blog from another website. See the Facebook help pages if you want to find out how to do this.
This is great, but after a blog post had been imported as a note, Facebook users are likely to comment on it in Facebook. If you are using blogging with WordPress and want to have all your comments in one place, there is a WordPress plugin that can help you: Facebook CommentsTNG. It will automatically scan your Facebook notes for imported WordPress blog posts and bring the comments back into WordPress.
This is an excellent plugin which builds on the idea of the Facebook Comments plugin, which no longer works (probably due to changes in way Facebook notes are marked up).
Check out the author’s page for the plugin: Facebook CommentsTNG.