Microsoft has released a fresh version of Windows 8 release to manufacturers (RTM) for MSDN subscribers. For those who are Windows 8 developers but not subscribers, Microsoft has also released a 90 day evaluation version of Windows 8.
Still slated for release on October 26th, this is the final version of Windows 8.
A few notes about the 90 day evaluation copy is that it can not be upgraded and, obviously, will expire. To upgrade, you'll need to uninstall the evaluation copy and a non-evaluation version of Windows 8 must be installed.