UniveRSS is a application being used as a WPF showcase by Microsoft. It represents your RSS feeds as a uiniverse of rotating cubes, the size highlights the number of unread articles. Comes complete with source code.
Unfortunately my Vista box is out of action at the moment, so I can’t try it out. In practice, I’m not sure how this will work as busy feeds like Boing Boing or Slashdot will dominate the interface, while personal blogs, which may be more interesting, won’t be as apparent. The question is to how to address the noise to relevance ratio issue.