Frank Pohlmann posted an article on IBM's developers site regarding the FreeBSD OS. Here's a short introduction:
The FreeBSD operating system is the unknown giant among free operating systems. Starting out from the 386BSD project, it is an extremely fast UNIX®-like operating system mostly for the Intel® chip and its clones. In many ways, FreeBSD has always been the operating system that GNU/Linux®-based operating systems should have been. It runs on out-of-date Intel machines and 64-bit AMD chips, and it serves terabytes of files a day on some of the largest file servers on earth.