Microsoft released their Windows Web Server 2008 RC0.

Overview

This time-limited release of Windows Server® 2008 Release Candidate will expire on April 7, 2008. After this time, you will need to uninstall the software or upgrade to a later release or a fully-licensed version of Windows Server® 2008.

This product requires a valid product key for activation – you may install the product without activation, but if you do not enter a valid product key and activate within 30 days of installation, the software will cease to function.

If you have received a product key via email confirmation, you may use the key with the software you download from this site or with a DVD containing Windows Server® 2008 Release Candidate.

If you have not received a product key, you can obtain one by visiting one of the following sites:

Developers
IT Professionals

Some copies of this pre-release software do not include an updated “Privacy Information for Installation Features” document. The correct document can be read online here.

Below are the download pages:

Windows Web Server 2008 RC0.
Windows Server 2008 RC0 Standard Edition
Windows Server 2008 RC0 for Itanium-based Systems – English
Windows Server 2008 RC0 Datacenter
Windows Server 2008 RC0 Enterprise
Windows Server 2008 Release Candidate: System Requirements and Installation Documentation
Windows Server 2008 Step-by-Step Guides
Windows Server 2008 Technical Overviews
Release Notes for this Release of Windows Server Virtualization
Windows Media Services 2008 for Windows Server 2008 RC0