Great resource for those who want to spin up a test server, but don't want to go through the installation and configuration steps. The list of images is particularly useful, and should be bookmarked:

Via Angus:

http://blogs.msdn.com/angus_logan/archive/2007/06/22/want-a-microsoft-office-sharepoint-server-moss-2007-virtual-image-vhd-vpc.aspx or www.microsoft.com/vhd

and the full list of images for download:

http://www.microsoft.com/downloads/results.aspx?pocid=&freetext=msvhds&displaylang=en

And for Partners that would like to distribute software in VHD format:

http://www.microsoft.com/windowsserversystem/virtualserver/partners/vhdpartners.mspx

Source: Nick Mayhew - Reaching out to partners in Australia : Virtual Disk Images for Download