Virtualizing

So I'm sitting here tasked with checking out virtualization. Sure I've used MS Virtual PC's and Servers for my MS Training courses. I was pretty good at loading them and using them. But really not the ideal platform for real life use. So off on the search I go!

So what to use? Xen, Citrix, VMWare, Microsoft or other? Wow, who just through the bag of skittles into my search?

So what am I looking for? Free, inexpensive, easy to learn, setup and manage Virtualization Desktop that can manage Windows XP-7, Mac Tiger-Snow Leopard, and Linux Ubunutu, SUSE, Red Hat and most others, not including FreeBSD. Really I don't think I'm asking for too much. This is only going to run a small section but hey I want what I need!