Shortly after completing the original Portal I spent some time exploring the origins of the game and much of the backstory. Anyone who has ever looked into Valve and their ways knows that there is always content that they don't include in the game, all available for those who are interested. In this case, it had a lot to do with the origins of everyone's favorite robot-powered testing facility.
As the game was being developed the designers worked out what had happened in the past to bring Aperture to where it is now. They released this information on the official website for the "company" through a series of DOS commands. Now that Portal 2 is right around the corner, they have compiled this information into an easy-to-follow timeline.
It starts off with shower curtains and ends with a psychotic operating system that is self-aware killing everyone in an attempt to beat Black Mesa. Hit the link for the full corporate history. You'll enjoy it for sure.