• VMWare Server

From author's site:

Virtualization is a technology that can benefit anyone who uses a computer, from IT professionals and Mac enthusiasts to commercial businesses and government organizations.

In essence, virtualization lets you transform hardware into software. Use software such as VMware ESX to transform or “virtualize” the hardware resources of an x86-based computer—including the CPU, RAM, hard disk and network controller—to create a fully functional virtual machine that can run its own operating system and applications just like a “real” computer.