Recommended Security Hardening Procedures

I am compiling a list of security hardening procedures which should be performed to a server, with the goal of coming up with a comprehensive list of hardening procedures which should be implemented.

The following lists the details I have compiled so far. Please feel free to contribute additional hardening tips so we may come up with a full and thorough list:

Install mod_security
Install mod_evasive
Install mod_limitipconn
Install APF
Install BFD
Install PRM
Install SIM
Install portsentry
Install chkrootkit and configure reporting cronjob
Install rkhunder and configure reporting cronjob
Install snort
Install tripwire
Install libsafe
Install mail header patch to identify cause of spam sent through nobody
Limit compiler and fetch utilities access to root only
Correct folder permissions to prevent directory transversal
Remove unneeded OS packages
Upgrade kernal to latest OS release
Ensure MySQL password is set
Ensure OpenSSH protocol is only using protocol 2
Ensure cannot SSH directly to root. Must SSH to admin first.
Enforce noexec & nosuid on temporary directories /tmp and /var/tmp
Disable used services
Disable DNS recursion
Disable IP source routing
Disable IMCP redirect acceptance
Disable certain php functions (system, exec, shell_exec)
Enable IP spoofing protection
Enable Spoofing protection
Enable syncookie protection
Enable misc. sysctl settings
Harden host.conf