OK, this is really cool. As of today Microsoft is providing virtual hard disks with evaluation versions of Microsoft Software pre-installed. This means that you can download virtual machines and try out complex server software without the need to set up anything.
Further to this Microsoft is providing a way for partners build their own software evaluation virtual machines with Microsoft software.
For more details go to: http://www.microsoft.com/technet/try/vhd/default.mspx