If you, like me, have been anxiously awaiting the release candidate build of Windows Server 2008, the wait is over!! Windows Server 2008 RC0 can now be downloaded from the TechNet BetaCentral web site. From here, you enter your Windows Live ID and pick the edition of Windows Server 2008 RC0 you want to test - Datacenter, Enterprise, Standard, Web Edition, or Itanium. A brief comparison between the Windows Server 2008 editions can be found here.
Once you select the edition you want to test, you will get a product key and a link to download the ISO file that you can burin onto a DVD and install on your test machine. You can also take the ISO file of the x86 version and using Virtual Server 2005 R2 SP1 to test in a virtual environment.
Check out additional technical resources at the Windows Server 2008 Technical Library on TechNet. These will help you get up to speed on Windows Server 2008 a lot quicker.