Microsoft have released Windows Server 2012 R2 Preview, Windows Server 2012 R2 Essentials and Hyper-V Server 2012 R2 Preview today.
They can be downloaded from the following links:
Windows Server 2012 R2 Preview
Windows Server 2012 R2 Essential Preview
Microsoft Hyper-V Server 2012 R2 Preview
The other noteable release is the Remote Server Administration Tools for Windows 8.1 Preview
http://www.microsoft.com/en-us/download/details.aspx?id=39296
With Windows 8.1 scheduled for tomorrow it’s going to be a busy week….