In the notes widget... or application, whatever facebook calls it. There's an option to import your feed.
Go to ads & pages
choose edit page next to the one you want to add a feed to
scroll down the page to the Notes box (I think it's about half way down the page)
click the little edit pencil and a drop down comes up, click edit options
that should bring up the notes application for the page, on the right hand side there's a box that says Notes Settings and in that should be a clickable Import a Feed or Import a Blog
click that and save the changes ... ta-da you've got a feed on your fan page
Of course that only allows you to add one feed. I think there are other applications out there that allow you to import other feeds if you need to.
Hope that helps!