The Windows 8 Developer Preview is now available for download on Windows Dev Center, this is a pre-beta version of Windows 8(and is for production environment mainly). What gives Windows 8 an edge over predecessor Windows 7 is that, Windows 8 is a tablet oriented operating system and has a very friendly and interactive interface for tablets/touchscreens while being equally good with normal PCs(ones with a Keyboard and a Mouse). The download is available here which includes the prerelease software. Since this a preview, many new features still need to be implemented(and some might get removed too) and do remember, this release is not really very stable. Folks at Ars Technica have written a nice Hands-on article on the prerelease software, check it out here.
Also, if you will like to experience a similar interface on your Windows, then you can check out Omnimo UI(Which is used with Rainmeter), its actually pretty good in giving you a Windows 8 like interface and even I use it.