Apt-proxy

I discovered apt-proxy today. Like a standard HTTP proxy, it caches files (packages) requested, but as it understands that what it's downloading is for apt, it can intelligently delete out of date packages. Since I've got Dapper installed on 3 PCs now, this should save me a fair bit of time and bandwidth. Apt-proxy is running well on my old 500 MHz server (which has Ubuntu Breezy on it).