In line with the previous post, here is an interesting project called Xen. Essentially, it is the result of years of OS research on virtual machines and nano-kernels. It is a VM or monitor that allows other, properly written, OS’s to run on top of it. This allows one to run more than one OS on the same machine, with excellent performance.
This has some obvious benefits. The biggest one that I can think of is security. If you divide your applications correctly, you can provide excellent containment. For example, if your web server gets hacked and it is running in a very limited hosted OS, the hacker cannot compromise your database OS and your email OS.
With CPU’s going multi-core, and CPU vendors working towards providing hardware support for this functionality, I expect this technology to become common in all hosting and corporate IT departments.