The Apple Lisa
The Graphical User Interface Gallery contains a tasty article on the development of the Apple Lisa OS. One amazing aspect to me is the iterations they went through before finalising on a simple iconic desktop. The image above is of a non-heirarchial faceted search, presented in what looks like a modern multi-coloumn view. Note though, that the modern multi-coloumn vie we have in Mac OS X for example is simply showing hierarchy, not a faceted search like the above image.
Via the Lukas Mathis' excellent Ignore the Code.