Sun VirtualBox

[dicion]

I run XenServer at work.

It's completely free for the basic version. It doesn't have all the livemotion and other features the enterprise one does, but it works pretty well for me.

[TexasComputerDude]

I really love virtualbox. I have been using it to practice freebsd and some other os's I'm learning. It saves me A LOT of time. So far no complaints that I can think of.