I am using buildout to automatically download and setup the many dependencies of my Plone installation. buildout more or less uses easy_install to download and install a bunch o
Here are instructions on how to setup your own PyPi mirror. The homepage of this project is here. There also seems to be a growing number of mirrors out there.
For instructions on how to setup your own package index, check out this blog post where one solution is explained at the end. Then you can also host your own internal packages in there. The advantage is also that the versions are fixed that way. (For a way to pin the versions directly in buildout, check out this post).
If there is only metadata on PyPI and the archive is stored somewhere else you might of course copy that over to your index as well. If you just use a PyPI mirror I assume that you still need access to these servers.