The Windows Server Division Weblog has the details:
Today our Windows Server product development team reached a very important milestone – the release of Windows Server 2003 R2 RC0. If you haven’t heard about R2 before, R2 is an update release of Windows Server 2003 with SP1, and provides improved branch office server solutions, identity and access management and storage management. You can get R2 RC0 from the R2 web site. Both x86 and x64 versions are available for download.
More by following the link and there’s also a Channel 9 video discussion. R2 is scheduled to be released by year end.