Kris Buytaert has just posted a great post on Virtualization.com: Looking Back at a Decade of Open Source Virtualization. While it's a lengthy article, it's definitely worth your read if you're curious about the history of virtualization, primarily desktop virtualization.
I come from Unix system administration background, and have been in this industry for just over 10 years – long enough to recognize all the names and technologies in the article and to testify: indeed, there were quite a few ways of running graphical desktop sessions remotely long before 2006 or 2007. Some of them are not as simple to use, but almost no technology stays stale – new approaches are being developed daily, and you couldn't be more spoiled for choice of desktop virtualization than you are today.
Have a look at the Open Source Virtualization reivew, I'm sure you'll like it.