"June is Bandwidth Conservation Month (well, not officially, but
let's say that it is), so if you have multiple machines running an
APT-powered Linux distribution such as Debian or Ubuntu, you should
take a look at apt-proxy, a utility that caches package downloads
in a shared pool for all interested parties on your LAN. This saves
you both the time and the bandwidth it costs to download the same
updates for more than one computer.
"I was blissfully unaware of apt-proxy myself last week when I
was upgrading three Ubuntu machines from 7.10 to 8.04, but the idea
of caching the downloaded packages seemed so obvious that I was
sure such a utility existed. After familiarizing myself with it I
decided to test it out on the next batch of package updates that
came down the wire..."