I predict that virtualization will be big this year. In line with this, I point you to a good tutorial on virtualization technologies available for Linux. IBM discusses the different types of virtualization and then outlines the various virtualization technologies available on Linux. In summary,

Virtualization is the new big thing, if "new" can include something over four decades old. It has been used historically in a number of contexts, but a primary focus now is in the virtualization of servers and operating systems. Much like Linux, virtualization provides many options for performance, portability, and flexibility. This means that you can choose the approach that works best for you and your application.

Whilst I am doing virtualization on the desktop, I am wondering if you guys have tried it on a production server. :)