I guess we all remember Jurassic Park, and especially one feature of this movie: The "Unix-system" with that cool 3D file-browser. Well that file-browser was SGI's 3D File System Navigator, which also helps us to know what that "Unix-system" really was, Irix.
For everybody who also wants something like this on his box I'd suggest to take a look at fsv, the 3D File System Visualizer.
It doesn't only display your filesystem in a cool 3D-view, it also gives you an optical representation of file- and directory-sizes.
Of course this is nothing for everyday's work, but it's a nice toy to show off to your friends. ;-)
So, when you ask yourself now where your files are, maybe they are somewhere at the back on the left side. ;-)