Microsoft has released Windows 8 Developer Preview build to public which can be downloaded.
Download Windows 8 Developer Preview Build NOW
http://www.askvg.com/download-windows-8-developer-preview-build/
Install Windows 8 Developer Preview Using VirtualBox or VMware Workstation
http://www.askvg.com/install-windows-8-developer-preview-using-virtualbox-or-vmware-workstation/