Facebook Connect. - wp plugin
If you read on facebook, in the developer center, it explains how to do this, and offers code snippets as well. First time I setup something for facebook on my wordpress website I just put the code into a widget and set the size accordingly, worked great for featuring my facebook page, but there's all kinds of other stuff in there as well for all the different things that you can do with your facebook account and the information that you can pull over to your blog.
Hope that helps.