Package Converter is an alien frontend . Alien is a program that converts between Red Hat RPM, Debian deb, Stampede slp, Slackware tgz, and Solaris pkg file formats. If you want to use a package from another Linux distribution than the one you have installed on your system, you can use alien to convert it to your preferred package format and install it. It also supports LSB packages.
The X Binary Package System (in short XBPS) is a binary package system designed and implemented from scratch. Its goal is to be fast, easy to use, bug-free, featureful, and portable as much as possible. There is a well documented API provided by the XBPS Library that is the basis for its frontends, to handle binary packages and repositories.
Upmf is a source-based package manager written almost completely in Scheme. The user is able to search, build, and remove packages. Since Scheme through GUILE is very extensible, the user can customize the procedures, or even exchange them with his own, if wanted. Packages are stored in their own self-contained directories and are incorporated into the filesystem with help of GNU Stow.