Built on Windows Server 2003 with Service Pack 1 (SP1), R2 takes advantage of the stability and security of a proven code base while extending connectivity and control into new areas. With Windows Server 2003 R2, you get improved: Identity and access management, Branch office server management, Storage setup and management, Application development inside and outside your organization's traditional boundaries

The R2 site on Microsoft.com is located here

You can register for R2 BETA 2 CPP here

The Windows Server 2003 R2 BETA 2 Reviewers Guide is published here