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.
Enforcer is a Linux security module designed to help improve integrity of a computer running Linux. The Enforcer provides a subset of Tripwire-like functionality. It runs continuously and as each protected file is opened its SHA1 is calculated and compared to a previously stored value. The Enforcer is designed to integrate with TCPA hardware to provide a secure boot when booted with a TCPA enabled boot loader. TCPA hardware can protect secrets and other sensitive data (for example, the secrets for an encrypted loopback file system) and bind those secrets to specific software.
Fritz!WRT is a set of patches to make the OpenWRT trunk run on AVMs Fritz!Box. Much progress has been made in recent OpenWRT revisions in the AR7 port, but it's still not running on the Fritz!Box. The patches also have the potential to make the T-Com SpeedPort run, because its hardware is very similar to that of the Fritz!Box. There are patches for the bootloader, LED support, and watchdog support, as well as KGDB support.
iloog is a Gentoo-based live CD targeted mainly at students and scientists. It features UnionFS filesystem support that enables you to write everywhere on the LiveCD and install extra packages, a graphical X environment through the Fluxbox window manager, many programming editors and IDEs, and a plethora of scientific applications, including Octave, Namd, Merlin, and full (La)TeX support.