Yes you can download Windows 8 for free from Microsoft Website and try it. The Windows 8 is available as of this writing from Microsoft website in a .iso file format. There are separate downloads available for 32 bit and 64 bit versions. This Windows 8 once installed will be labelled as Windows Developer Preview and will provide you various new features such as new windows explorer, improved internet explorer, improved ribbon interface, metro style applications and much more.
In case you are still wondering how to download Windows 8 from Microsoft website, this post will help you with that. Open up another browser window and visit your search engine and search for Windows 8 Download from Microsoft. You should see the first link from microsoft providing Windows 8. As of now the Windows 8 will be displayed as Windows Developer Preview which is almost as good as Windows 8. The beta version of Windows 8 is expected to be launched in Feb 2012.
Windows App Store will not work in this free download from Microsoft for Windows 8. The Windows 8 application store is expected to offer Metro Style applications just like mobiles offer free and trial applications to download. You can even run this Windows 8 using VMWare player, however Microsoft Virtual PC will not support this Windows 8.