Cache Ubuntu Update to Speed Up Update and Save Bandwidth

If you have several Ubuntu machines at home, every time there is a new package, you will need to download the same package several times.
Just found out a package called squid-deb-proxy.  You will need to have a server and install

sudo apt-get install squid-deb-proxy avahi-utils

and in other machines install:

sudo apt-get install squid-deb-proxy-client

From now on, "avahi" on the server will advertise the proxy server in your network.
And when you download any package from any of your local machines, it will see the proxy server and download the package through the server.

[via: http://castrojo.wordpress.com/2010/02/28/zeroconfing-squid-deb-proxy/]