OnThaRoadAgin is right - Networked Blogs is what you want, but there is another step. First you have to sign up with them on Facebook (register your blog) - that will enable them to pull your blog posts and post them to Networked Blogs, so that people who "subscribe" to your blog through them on Facebook will get your posts that way (it's sort of like an RSS feed exclusive to Facebook)......
BUT to have them automatically post to your wall you also need their Application.
I tried using their App but had trouble with it - it was causing my Fan Page to come up completely blank, so I abandoned it some time ago and just post to Facebook manually now. I may give it a try again in the future, but for now it only takes a minute of my time to do it manually.
There are some WP plugins that will do pretty much the same thing, but I haven't tried any yet. As TWE grows and gets busier, I may have to resort to one of them.