As many sources have already reported, a new wave of betas, aka previews, of the Windows Blue Server generation, i.e. 2012 R2, are available for download as of 06/23/2013.
The whole list of goodies can be found here: http://www.aidanfinn.com/?p=15051
As this author, and MJF (http://www.zdnet.com/microsoft-starts-rolling-out-blue-previews-of-windows-server-sql-server-7000017242/) report, the downloads are available for MSDN and Technet subscribers.
Hardly anyone mentions though that the previews are available for other Live-ID users as well. Here the link: http://technet.microsoft.com/en-US/evalcenter/dn205292 I could successfully download the Essentials R2, try for yourselves the others.
Evaluate, learn, test and enjoy!