Years ago many of our networks were managed by Microsoft Windows but, today *NIX systems are growing in popularity in the server room and even in our own home. I and the majority of users on the TechCafe network use Linux from surfing the web to hosting servers. If you have not played with a Linux operating system, then I recommend giving it a try. ITS FREE, so why not?
Ramesh has put together 50 UNIX / Linux sysadmin related tutorials that I recommend bookmarking.
My favorite flavors of Linux: