Scouring the net for virtualization solutions similar to what I use on my Mac, I found an Oracle DBA's blog entry on how to install Xen on CentOS 5.0.
Whilst the article seems simple to follow, nothing still beats the simplicity and ease of installation of VMWare and Parallels – but hey, if it means saving big bucks, then I guess a couple of command-line typing isn't that bad.
Have you tried running guest operating systems on your Linux box?