The following links contain useful information about Linux.
Distributions
Ubuntu Linux - The fastest growing distribution by a wide margin. Ubuntu is a derivative of Debian with development financially backed by Canonical. Ubuntu is dedicated to offering a high quality, easy to use distribution free of charge.
Gentoo Linux - One of the best Linux flavors out there. Not for beginners, though. Please note that installing this distribution requires much more knowledge about linux than other flavors. Gentoo usually takes 2-3 days to install the first time.
Slackware Linux - Another great flavor, best for intermediate Linux users. Make sure to check out Dropline GNOME if you're going to use Slackware.
Debian Linux - One of the most popular flavors for more experienced users. The installer's getting better and apt is almost as great as portage is for gentoo.
Fedora - A free linux distro sponsered by Red Hat.
Mandriva Formerly MandrakeSoft, Mandriva Free is the current open source version.
Knoppix - The best LiveCD distribution available. Just drop in the CD and go.
Knoppix-STD - Knoppix for those of us a little more security conscious.
PHLAK - The Professional Hacker's Linux Assault Kit is another great LiveCD distribution for security minded individuals. A Morphix derivative with two flavors: Fat Man and Little Boy.
openSUSE - Sponsered by Novell, openSUSE is a general purpose OS. Release 11.2 should be available November 12th, 2009.
Yoper - Defined by its customizable optimizations.
Yellow Dog Linux - Based on Red Hat Enterprise/ CentOS.
Linux News
Footnotes - Your best stop for news on the Gnome Desktop Environment
Linux.com - Supported by The Linux Foundation, Linux.com is for linux related discussion.
Linux Gaming - Linux Gaming news
Slashdot - Not specifically Linux news, but one of the biggest news sources for computer and technology related issues.
Groklaw - The best way to keep up on all of SCO's unfounded linux lawsuits with all of the actual court documents.
Development
Linux Kernel Archives - Get the latest and greatest kernel sources straight from your favorite mirror.
SourceForge - The largest repository of open source code and applications for linux and windows. A great place to find the newest versions of linux software.
GNU's Not UNIX - The source for all of the GNU/Linux tools and the best place to find Richard Stallman's papers on the philosophy behind free software.
GNOME - Get development news or the latest gnome packages from the offical source.
KDE - The KDE homepage, for those who prefer Linus' desktop of choice.
Enlightenment - Yes, they are still working on the next generation of window managers, and they are maintaining a great lightweight window manager.