I have at least 3 machines running Debian on my network at any given time and I’m using Debian testing (currently Lenny) because it’s so close to being stable anyway. Still, there are plenty of updates on a regular basis and keeping my machines up to date is a rather big drain on my network connection considering that machines share basic packages anyway. I looked around and found a wonderful tool called apt-proxy which will act as both intelligent cache and partial mirror for machines on a network. You set up apt-proxy on one machine with the names of whatever package repositories you want to use along with a few other settings. I got some pointers from a wonderful article at Debian Administration by Steve when I was messing with the default config provided with the package. Once that’s all set up, you change all of the other machines’ sources.list point to the apt-proxy mirror you just set up. Then machines requests will get intelligently filtered through apt-proxy and duplicate packages will be cached for multiple machines. It’s great because it makes subsequent updates faster and simplifies mirror management on different machines. I could see this being very handy for clusters and doing large installs.