TrinityOS is a step-by-step, example-driven HOWTO on building a very functional Linux box with strong security in mind. TrinityOS is well known for its strong packet firewall ruleset, Chrooted and Split DNS (v9 and v8), secured Sendmail (8.x), Linux PPTP, Serial consoles and Reverse TELNET, DHCPd, SSHd, UPSes, system performance tuning, the automated TrinityOS-Security implementation scripts, and much more.
MonAMI aims to be a standard place for monitoring the availability and performance of services. It can talk to many different monitoring systems while remaining easy to configure. It has a plugin structure, making it easy to add new things to monitor or to integrate with new monitoring systems.