So I came across Xen and XenServer last night, and my eyes lit up like a small child on Christmas with a giant pile of presents under the tree.
I've long desired to have some form of virtualization setup at home, but vSphere requires virtualization support from the hardware, and Hyper-V likewise (plus, it's Microsoft, so @!#$ that). VirtualBox doesn't require hardware support, but it also has severe stability issues in my experience. It's just not stable enough to be used as the basis of a home cloud.
In contrast, Xen seems like a miracle given form. It can use, but doesn't require, hardware virtualization support, it's completely open-source, and it's footprint is ridiculously small. Furthermore, it's used by Amazon for their EC2 offering, and by Rackspace for their cloud hosting, so stability is obviously not an issue. Combined with the community support that inevitably arises around open-source projects, I'm rather elated at the prospects here.
Anyone have any suggestions for what to do once I get this thing going on some of my spare boxes? I've got a few ideas, but I'd love to hear yours as well.