Navigation Tools for Non-Hierarchical, Dynamic Web App + Agile Horizon

Howdy icksda!

I'm looking for recommendations or just some good discussion on designing interaction for a dynamic analytics web application with information hierarchies that mesh, but aren't always guaranteed to be a perfect hierarchy, and who's levels may change often.  I'm looking for patterns that can flex when content changes somewhat dramatically, while still providing a strong and intuitive framework for information seekers.  Things that come to mind are the usual suspects of spin-downs, trees, accordions, and fly-outs.  I'm also open to 'content-is-nav' ideas.

Thanks!

-Mike C.