Get your own copy of the Windows 8 Developer Preview directly from Microsoft here: [msdn.microsoft.com
I see that it requires a clean install, so you can either put it on its own machine or virtual PC. Also, I've heard that it isn't very stable yet, so I wouldn't use this as your primary OS.
Anyone tried it out yet?
There's a slideshow of some of the interface on the Microsoft news site: [microsoft.com