Windows 8 Release Preview
http://windows.microsoft.com/en-US/windows-8/release-preview
ISO files
http://windows.microsoft.com/en-US/windows-8/iso
Tools & SDK
http://msdn.microsoft.com/en-us/windows/apps/br229516
Visual Studio 2012 RC
http://www.microsoft.com/visualstudio/11/en-us/downloads#professional