You may have noticed the post on the SharePoint Team blog (http://blogs.msdn.com/sharepoint/archive/2008/08/18/update-on-virtualization-support-for-sharepoint-products-and-technologies.aspx) announcing support for Hyper-V based virtualization.  There are however many things to know about the extent of what is supported.  Obviously we will be supporting our own Hyper-V solution, but beyond that, we will also be supporting SharePoint running within SVVP certified solutions.  As of the time of writing this, we only have one partner that is SVVP certified, Novell, Inc.  The list is maintained at http://support.microsoft.com/kb/944987.  We do have a number of vendors who are working on becoming certified though, currently:
   Cisco Systems, Inc.
   Citrix Systems, Inc.
   Sun Microsystems
   Unisys Corp.
   Virtual Iron Software
   VMware, Inc.

If things go well, we will see more of these vendors go from one list to the other--which will provide you with more options to suit your needs.  None-the-less, this is an exciting time for virtualization and SharePoint, and only paves the way for bigger things.

As I mentioned before, there definitely are some things you should be aware of about running SharePoint in a Hyper-V environment.  From a technical perspective there are two large ones.  First, you need to be on SP1.  There's not much interpretation there--for support and licensing to line up, we are requiring that.  The second point is that you cannot take a snapshot of the Hyper-V environment.  This largely has to do with how a farm could get out of sync in many areas and not be able to be guaranteed to come back online properly if this was done.  In time my hope is that we can change this support stance and allow for more flexibility in this area, but for now, don't snapshot.