Office 2007 and Windows Vista are available on MSDN Subscriber for downloading at the moment. MOSS 2007 is available as a Trial version for 180 days from this site
"The Photosynth Technology Preview is a taste of the newest - and, we hope, most exciting - way to view photos on a computer" is what Microsoft LiveLabs has to say. Check it out for yourself here.
Trial version of HIS 2006 can be downloaded from the following URL. HIS is a tool for achieving integration with the IBM Platform. For more information on HIS visit - http://www.microsoft.com/hiserver/default.mspx
Check out the Beta release of Microsoft's Tag Space. Its a demonstration of tagging and bookmarking features from Microsoft which they plan to include for social bookmarking as part of all the Microsoft websites.