Navigation (again)

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