Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
Keryx is a portable, open source and cross-platform package manager for APT-based (Ubuntu, Debian) systems. It provides a graphical interface for gathering updates, packages, and dependencies for offline computers.
Keryx currently only works for Debian based Linux distros (but like I said, the packages can be downloaded from Windows or Mac OS X too), but there are plans for adding support for a number of other package management systems.