Tim Freeman over at GridVM.org has come across a great online virtualization for Linux overview guide.  This Tech Comparison was created by the KernelNewbies.org site. 

In the table, it compares the features and performance of the various virtualization technologies available for Linux.  They hope it explains why so many Linux distributions today ship Xen, even though UML and KVM are upstream and lhype is getting pretty close to inclusion into the upstream kernel.

Check out the chart, here.