gBootRoot makes the construction and development of distributions fun and simple with its Root Methods (Yard) and user-mode-linux test bed. Finish the product with a Boot Method (2-disk compression supported). Normal (non-root) users can make root filesystems and boot disks. It includes the make_debian script to create a testable user-mode-linux base Debian system, add-ons to enhance methods, and an MTD Emulator useful for running distributions made with the jffs/jffs2 filesystem.
A simple and trivial to use utility for keeping various 3rd party application packages installed on multiple machines. It leaves flexibility for making packages local to a host or remotely served from a central server. It is not the same sort of tool as RPM; rather it serves a related but different purpose. In particular, unlike most package systems, it can run independently of your main system (RPM, pkgadd, etc) and lets you install multiple versions of an appplication at the same time.
Owl (Openwall GNU/*/Linux) is a small security-enhanced Linux distribution for servers. Owl also makes a good base system for customized virtual machine images and embedded systems, and Owl live CDs with remote SSH access are good for recovering or installing systems (whether with Owl or not). A single Owl CD includes the full live system, installable packages, the installer program, as well as full source code and the build environment capable of rebuilding the entire system from source. Owl supports multiple architectures (x86, x86-64, SPARC, and Alpha) and offers some compatibility for packages developed for other Linux distributions. The primary approaches to security are proactive source code review, privilege reduction, privilege separation, careful selection of third-party software, safe defaults, and "hardening" to reduce the likelihood of successful exploitation of security flaws.
Mpkg is a ports collection. Each port contains the information necessary to automatically download, compile, and install a specific program, and also information about dependencies between programs. Ports collections are common on various BSD flavors, but mpkg is designed to be portable to any UNIX-like system. Development has been done on DEC OSF/1, GNU/Linux, and Solaris. Mpkg also tries to install all programs in separate directories, never touching the common directories like /usr and /etc.