Knoppix - A GNULinux distribution(not under the GNU
GPL) that can let you use GNULinux without any installation on your system.
You just have to your system from the CD cantaining the boot image.
Linux.org - This site is a must read anybody interested in GNULinux.
linuxexposed.com - A great site with a lot of stuff on networks &
security.
linuxguruz.com - Learn everything you want to, straight from the
Gurus.
RedHat.com - This is the official RedHat site. You can download
the latest RedHat version from here ABSOLUTELY FREE.
RPMFind.net - This is a site where you can find most of
the GNULinux rpms. that are needed by you.
Slackware.com - Site of Slackware distro of GNULinux.
