Debian just keeps rocking. In this week's Debian Weekly News, there was a short blurb about
apt-cacher. It allows one machine to serve a local cache of "needed" updates/upgrades, and all of the client machines can pull from it. If a package is requested that the cache machine doesn't have, then the new file is transfered to both the cache and the client.
The entire set-up process, from apt-get install apt-cacher on the cache machine to apt-get upgrade on the client machines, took me approximately 5 minutes.