Are you like me and have multiple Ubuntu machines under one roof? Are you tired of downloading the same update multiple times? Sick of what seems to be duplicate work? Let me introduce you to my little friend... squid-deb-proxy.
Squid-deb-proxy is a new package for Ubuntu 10.04, and it's designed to make your life easier and allow faster updates if you manage more than one Ubuntu machine. Conceptually, squid-deb-proxy consists of two pieces, a client and a server. The server package is "squid-deb-proxy" and the client package is "squid-deb-proxy-client". The "squid-deb-proxy" server package is basically a squid caching server, with an out-of-the box configuration that allows it to cache .deb packages and make them accessible to the local area network. The "squid-deb-proxy-client" package is basically an include file to your standard apt configuration that makes apt aware of the squid-deb-proxy.
To install the server, simply "sudo apt-get install squid-deb-proxy avahi-tools" on the machine that you wish the server to be on. This will install the squid caching server and the avahi (Bonjour) auto-configuration network utilities, and start both servers, so your new caching squid proxy will start broadcasting its availability on your network. Then, a "sudo apt-get install squid-deb-proxy-client" on each Ubuntu 10.04 machine (including the squid-deb-proxy server) will install the apt configuration. You'll want to install the client on the server as well, so whenever the server downloads updates those updates get cached by the squid proxy. This will also allow the server to install already-fetched updates via the proxy.
Once this is done, squid-deb-proxy is transparent to the user. Each machine's apt program will look on the network for a squid-deb-proxy, and if it finds one, it'll pass its requests through that. The proxy will cache any .deb packages that come through it, and make them available for the next update client that needs them. The second client to request these same updates will pull them down from the squid proxy, rather than having to get them from the Internet. You get the benefit of a local repository without the hassle of setting one up!