The June CTP of Windows Server 2008 is available. This is a post beta 3 release and has a couple of new features. The most noteworthy new feature is the availabilty of the web server role (IIS 7) on a Windows Server 2008 core installation. More info about that here. You should know that not all features of IIS 7 are supported. For example, ASP.NET is not supported so you cannot have something like Windows SharePoint Services 3.0 on a server core installation.