Here is a very cool article on Microsoft's Open Source Lab.
Microsoft’s Open Source Software Lab is an ambitious research project. Located on the company’s main campus, the lab houses more than 300 servers, which collectively run more than 15 versions of UNIX and 50 Linux distributions. It boasts a team of senior-level programmers and system administrators, some of whom were architects of popular Linux distributions or authors of well-regarded books. In short, the lab is one of a few such facilities in the world dedicated to open source research.
