debcache script is designed for reasonably
easy maintenance of multiple (or a single) Debian-based machine
where the desire is to reduce network bandwidth.
The best exemplar of the usefulness of the script is when you have four machines running OpenOffice, and a new 200 MB download comes out; perhaps that would take you two hours to download for each machine if you are as miserably connected as I am. With debcache I can do all the downloads I need at a remote location, just once. A full cache for four of my current machines (three Ubuntu, one Debian) is about 2 gigabytes, or about half of my cheap USB stick. A full update normally takes about two minutes, and then I have fresh software for all of my machines.