Linux Learning Sites
http://www.linuxhomenetworking.com/
http://www.server-world.info/en/
http://www.howtoforge.com/centos-5.1-server-lamp-email-dns-ftp-ispconfig
http://www.linuxsecurity.com/
http://www.linux.org/
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/
http://www.sans.org/top20/ (Security related)
http://linux.sys-con.com/read/46186.htm (BEST PRACTICES)
http://www.scottklarr.com/topic/115/linux-unix-cheat-sheets—the-ultimate-collection/ (cheat sheet)
http://www.frsirt.com/english/services/ (0 day exploit)
http://www.securityfocus.com/unix
http://www.securiteam.com/exploits/
http://www.deter.com/unix/
http://insecure.org/sploits_all.html
http://insecure.org/sploits/ping-o-death.html
http://www.linuxquestions.org/
http://tldp.org/
http://dag.wieers.com/rpm/FAQ.php#B2
yum whatprovides mod_access.so