Navigation based on directed graphs (conceptual maps or similar)

Dears
I am developing a drupal 5.1 site for Computer ethics concepts.
I am structuring information as Concepts and relations. I defined the necessary node types and some views. It works quite nice.
But in order to provide a better understanding of the site structure I will need some graphical support.
The idea is to provide a graphical site map of the concept structure and navigate using this map (something similar to CMAPS BUT DINAMICALLY BUILD depending on the evolution of the site). Obviously this is not a usual sitemap.
Any idea or help?
Thank you!
José