Something to add to your list is pkg-cacher done by Robert Nelson. pkg-cacher is a modified version of Debian's apt-cacher that works with .rpm and .deb packages. He made it as a helper application to vzpkg2... something he also wrote as a replacement to OpenVZ's venerable vzpkg application.
vzpkg2 and pkg-cacher are used to build OpenVZ OS Templates by dragging packages from the distro repos into a local cache.
pkg-cacher has a number of unique features especially since it can do both rpm and deb repos so anyone needing such a tool should check it out. It can be a stand-alone service or a CGI application.