VMWare Player
VMWare realized a Player version of there virtualization software: VMWare Player. Basically it is a version of VMWare that let you do almost everything except creating new Virtual Machine. The good point is that it comes for free. And even better you can download optimized, preconfigured virtual machines coming with applications from IBM Software, Oracle, BEA, MySQL, Red Hat, Novell, and others, from the VMware VMTN Virtual Machine Center. You might download the player on this page.
I am curious to see Microsoft reaction with Virtual PC.