It's been for a while that I had been looking with envy at VMWare users when I was about to setup some sort of testing environment. All those folks had to do was to go to VMWare's Virtual Appliances Repository and pick the VM that suited their needs.
Me, on the other hand, had to go through cloning VHDs, SYSPREP-ing VMs, customizing and installing all those applications just to get going (well, I do have some home made generic VMs, but you can never know what the requirements will be the next time you need to create some virtual environment).
Finally the Virtual Server users are getting there ! Microsoft has just announced their "VHD Test Drive Program" initiative (read more about it here). To get the long story short: you can download pre-installed virtual machines from Microsoft's site and play around with all those new technologies you want to evaluate or learn about.
The catalog of the available VMs can be found here: http://www.microsoft.com/technet/try/vhd/default.mspx and though currently it contains only Windows Server 2003 R2, Exchange 2007 and SQL 2005 VMs, I hope that with the time it will grow to span more and more technologies.