OK, I’m late on this one (like usual), but here it goes:
Virtual PC 2007 has been released for download here.
Virtual PC is available free for Windows XP and Vista Boxes (note the limitations on which versions are “supported”). I haven’t seen any downloads for the Virtual PC Tools for Unix variants, but they have been available (in a beta form) from Connect.
For more information, see the full Virtual PC site here.
Also note that a newer version of VMWare Workstation (+ Player) was posted recently that provides better Vista support on both the client and the “server” side. Go to VMWare for more information.