NetNewsWire is a RSS reader for the Macintosh that uses the standard three-pane interface. I think it's the best RSS reader out there.
However, not everyone is enamored of the three-pane interface, and some would prefer a three-column interface (much like Mac OS X's column view).
Well, this guy has managed to pull it off: Widescreen NetNewsWire. It's a really, really, really neat hack, and it's really easy to do.