+1 for Linux (Re: And sharing malware in 5 4 3)
Which distros provide this? Anything for Debian? I'm sitting here looking at a lot of packages in /var/cache/apt/archives. There's apt-cacher and apt-cacher-ng for Debian and derivatives, but those involve explicitly setting up a server and clients. There are also various ways to mirror repositories.
I'm wondering how easy it would be to get apt-cacher running on pfSense, but that seems like a lot of effort for a home LAN – not that many instances of Linux and a reasonably fast Internet connection. If there's a simple setting I can change, or a package I can install, to get peer-to-peer sharing that would be worth it.