Other virtualization options

[Lazybones]

VMware might be king of the enterprize market, but I was surprised how far projects like virtualbox have come. It even supports a mixed desktop mode like parallels does on the mac, which is really neat.
http://www.virtualbox.org/

[Shayne]

I was trying to use this for a while and I found it to be fairly unstable.  At times just minimizing a virtual machine would cause my entire OS to freeze entirely.  On my windows box I use the equally free VMware Server.

I actually purchased a license for Parallels due to the mixed desktop.  I use it at our RPG sessions to run Excel and OneNote.

[Tom]

I used to find VBox unstable. But as of late, on linux its ultra stable, and quite a bit faster than VMware Server.