Debian archive proxy and partial mirror builder apt-proxy automatically builds a Debian HTTP mirror based on requests which pass through the proxy. It's great for multiple Debian machines on the same network with a slower internet link. The archive is automatically kept up to date using http, ftp or rsync. Cache cleaning of unused and old versions is configurable. You can also import the contents of your apt cache into the archive using apt-proxy-import.
This will install all the needed packages. You might want to install rsync and dpkg-dev. You need dpkg-dev only if you want to merge a local apt cache to apt-proxy. rsync package is only needed, if you want to use rsync to download packages.
After the installation of apt-proxy is complete you have to edit the /etc/apt-proxy/apt-proxy.conf file. Mainly you add all your local apt sources you have.