Sysinit is a system-initialization scheme for use with Linux and a daemon-management scheme for use with runit or daemontools. It provides a common interface to all functionality, and uses envdirs instead of sourced shell scripts or custom configuration files. It does error handling, handles dependencies gracefully and simply, and handles runlevels.
Zen Garden is a tool that watches over the installation and building of source archives. It is a fork of installwatch that has been heavily updated with modern features. It can prevent build tools from interfering with files outside the build directory and create a virtual chroot to perform installations in or backup the files the install overwrites.
EPOR is an extensible package organiser for Unix-like systems. It's written to trace filesystem changes (something being installed) and save this information in a simple text database (this, as any other provided feature, is customisable via the embedded Guile interpreter). Database entries contain information supplied by the command line (package name, version, etc.) and traced by filesystem changes (new directories, files, etc.). This is achieved using the "LD_PRELOAD method''.
Gentoo Category Select is a graphical tool for selecting Gentoo Package Categories to exclude from your local package repository. It does so by weaning information from multiple directories and files for convenience, as well as providing warning about categories that should not be excluded due to currently installed packages. This is achieved without the addition of a configuration file. Currently only the Qt front-end is finished. It is modularly designed for ease in creating front-ends based on other toolkits. The advantages are saved disk space (small/MMV), quicker rsync time (small/MMV), and a lessening of bandwidth requirements by gentoo.org and its mirrors.