Microsoft confirms Windows 8 has been released to manufacturing, OEM partners now have final code

http://www.engadget.com/2012/08/01/microsoft-windows-8-rtm/

Another interesting bit is:
Microsoft showed off its answer to Linux 'Live CD' distributions - entire operating systems which run off a CD, DVD or USB stick with no installation required - with Windows To Go. Sold as a 32GB USB drive, Windows To Go allows any Windows 7 computer to boot into Windows 8 and retains the user's installed applications, files and settings. Pricing for Windows To Go has not yet been confirmed.