If you can’t wait for mozilla to release V 1.0 of their Firefox browser with its in-built RSS reader, you can always download Sage – Sage is an Extension for Firefox which creates a Sidebar (available under View -> Sidebar -> Sage) allowing you to browse your RSS sites from within the browser.

There is also an import function which is supposed to allow you to import your RSS Feeds from your RSS Reader apps although I couldn’t get this to work with either NetNewsWire or Shrook OPML files.

See screenshot below to see it in action: