IBM’s developerWorks has a new article that covers the basics of the many virtualization options for Linux:

Virtual Linux: An overview of virtualization methods, architectures, and implementations

“This article explores the ideas behind virtualization and then discusses some of the many ways to implement virtualization. We also look at some of the other virtualization technologies out there, such as operating system virtualization on Linux.”

http://www-128.ibm.com/developerworks/library/l-linuxvirt/index.html