Linux is my preferred OS. It's fast, powerful, and free. What's more, it's just fun to work with. I'm fortunate to work for a company where I can run Linux on my desktop. If I ever have to downgrade to something else for a future job, it'll take a lot getting used to.

For those unfamiliar with Linux it's a full-featured, POSIX compliant, UNIX-like operating system. My distribution of choice is Red Hat. They make a fairly standard packaging that you can download for free or buy for about $40.