Navigation (again)

System

What lightweight facilities have you implemented successfully to allow users to define/override default navigation? I know this has come up before but I think it deserves reconsideration.

We are thinking of implementing a navigation scheme based on the information architecture of the site - each content element has a metadata property that lets the user define it's nav title and whether or not the item should appears in navigation, and the navigation is automatically/dynamically created based on folder structure, file contents and metadata. I've done this in the past and it seemed to work pretty well when there was a close relationship between IA and UI.

There are some cases where the navigation shouldn't match the folder structure at all. This is more like the general case of "how do I let users declare navigation" when the navigation does not match the IA.

What are people using successfully to let non-technical users define navigation? or what existing URLs describe this subject?

TIA,

-John