Linux is a free operating system that is competing with Windows and Macintosh. It is primarily used for servers (most of the web runs on Linux), but is becoming very popular on people's home computers and is already more common than Macintosh on home desktops.
Slashdot: News for nerds, stuff that matters - A self-explanatory subtitle. One of the most popular sites on the entire web to boot. I visit it several times a day, as well as its gaming section. Covers news about all technology and all operating systems (mostly Linux and Windows, though there's a fair amount of Macintosh news too).
My personal guide to the command line for newbies
Easy URPMI config for Mandrake - Helps you set up URPMI to automatically download and install almost any Linux program on command. If you're unfamiliar with URPMI, this is how it works: 1) You type the command for what you want to install. For instance, to have it download and install gaim for you just type "urpmi gaim". 2) Watch it download and install the program and any required packages. 3) Enjoy. It's a fantastic program. It's counterpart, URPME, will uninstall programs and automatically uninstall dependant programs. The "I" in URPMI is for "Install", and the "E" in URPME is for "Erase". The "RPM" just stands for RPM, the standard for Linux installation distribution, and I have no idea what the "U" stands for.
IBM's Windows-to-Linux roadmap - Intended for developers, but anyone wanting to learn more about Linux will find it informative.
Linux Dictionary - Just what it says. A very large reference.
Linux Files and Command Reference - Last updated June 1, 2000, but should still be accurate in most things.
UNIX/Linux command line tutorials - Looks even older than the above link, but should still be accurate in most things.