I have a blog that I started before I joined FB. You can either use the "link" button on your status update or if you have a blog entry you think other FB friends would be interested in specifically use the "link" button for that particular entry. Does that make sense?
However, I have found that very few of my FB friends ever come over to my blog (except the ones who already visit my blog pre-FB days) when I link it so I stopped. It's never hurts to try - perhaps you'll have better luck than me.