One of my colleagues, who has been playing with Plone recently has come up with an idea that is absolutely breath taking in its simplicity:
Use plone, which is a web content manager as a software archive. You can upload disk images as documents, add descriptions and structure the information. Given that what we wanted out of the software archive was a solution that, to users, looked a little like mirrorservice.org but was easy for the people managing to add information about packages and software to it - seems ideal
After all we're just managing content.
Wish I'd thought of it (green with envy)...