Few weeks ago Windows 8 RTM was available on MSDN and TechNet sites but Windows Server 2012 wasn’t, although they RTM’d on the same day. Today it has been made available through MSDN & TechNet subscriptions and other volume license channels.
Windows Server 2012 is the server version of Windows 8 and successor of Windows Server 2008 R2. It comes with redesigned Server Manager leveraging new Modern UI unless installed in Server Core mode. It’s worth to mention that Windows Server 2012 has no support for Itanium-based computers.
So, if you’re an MSDN/TechNet subscriber, you can go ahead and download it. All versions have been made available along with the keys.
You can also download a free evaluation of Windows Server 2012 (ISO and VHD) for 180 days from the TechNet Evaluation Center.