It is not something new, but for me VMware is new.
I have since some month ago started to use VMware workstation (I was not so expensive to buy), there is also a free version called VMware player.
"VMware Player lets you evaluate new or pre-release software contained in virtual machines, without any installation or configuration hassles. You can also share existing virtual machines with colleagues or friends—just use VMware Player to run any virtual machine."
VMware has helped me lot as I often as developer/architect have to install new software, updates..
After a while my PC is completely over installed with different servers and became slower and slower.
The last months I have working with architecture for mobility at one my customers, this architecture also includes Mobility Management server and Security Servers. All these servers we need if we have a lot of users/devices out there.
So with VMware I am able to install a new server (linux or MS server 2003) on my laptop and have it well integrated with my developer environment (Netbeans/Carbide.j). It is really good not have to install all different servers direct on my laptop OS and to be able to test new version before you upgrade the real server.