MSDN Virtual Labs
Just saw this post by Jan Schreuder talking about MSDN Virtual Labs. If you haven't checked these out yet, it's worth it. Without installing the software, try out various Microsoft technologies, both present and future. If you were just dying to try out that new SQL Server 2005 feature, or find out what Windows Workflow Foundation is really all about... look no further than MSDN Virtual Labs!
From what I can tell, MS has set up some boxes with Virtual Server hosting images of pre-built machines containing various technology combinations. You use the web client to RDP to these machines, providing a reasonable remote control experience. You actually get administrator rights to the machine, allowing you freedom to try various things without being hampered by security. And I'm guessing that the machines are set up in undo mode and don't save state - so that the next person gets the same baseline machine as you started with. Cool!