The final, shipping version of Windows Server 2008 R2 is now available for download. Those with MSDN or TechNet subscriptions can get the full version (Web, Standard, Enterprise, Datacenter, and Itanium), while anyone is free to download an evaluation edition:

Windows Server 2008 R2 builds on the award-winning foundation of Windows Server 2008, expanding existing technology and adding new features to enable organizations to increase the reliability and flexibility of their server infrastructures. New virtualization tools, Web resources, management enhancements, and exciting Windows 7 integration help save time, reduce costs, and provide a platform for a dynamic and efficiently managed datacenter. Powerful tools such as Internet Information Services (IIS) version 7.5, updated Server Manager and Hyper-V platforms and Windows PowerShell version 2.0 combine to give customers greater control, increased efficiency and the ability to react to front-line business needs faster than ever before.

Remember that Windows Server 2008 R2 is available only in x64 (and Itanium); there are no 32-bit versions.