Distros
http://distrocenter.linux.com/
http://fedora.redhat.com/
http://www.debian.org
http://www.mandriva.com
http://www.suse.com
http://www.slackware.com
http://www.ubuntulinux.org/
http://www.distrowatch.com
http://www.openbsd.org
http://www.freebsd.org
http://www.netbsd.org
Software
http://www.rpmfind.net
http://freshmeat.net
http://httpd.apache.org (apache webserver)
http://www.mysql.com (mysql database)
http://www.postgresql.org (postgresql database)
http://www.samba.org (unix file sharing from/to windows neworks)
http://www.proftpd.org (ftp server)
http://www.php.net (open source scripting)
http://www.styx.demon.co.uk - unix sms client
http://people.ee.ethz.ch/~oetiker/webtools/mrtg/ (MRTG, Traffic grapher)
Window Manager
http://www.kde.org
http://www.gnome.org
http://www.x.org
http://www.xfree86.org
Help
http://linuxdoc.org
Security
http://project.honeynet.org
http://www.linuxsecurity.com
Misc
http://kernel.org
http://www.sunfreeware.com
http://slashdot.org (news)
http://bb4.com - Big Brother monitoring