Advanced drupal 6.x hierarchical taxonomy list pages
A good quality taxonomy listing page can act as a really good sitemap. Good sitemap pages are great for internal linking effects that helps visitors browse your site, and coincidentally aids in SEO. Most (?all?) nodes will have taxonomy terms attached to them. Hence it's a pretty good start to aid someone to browse your site. The problem is the core taxonomy module doesn't make good quality listing of taxonomy terms. For instance it ignores the term hierarchy, it doesn't display links to child term pages, etc.
The directory module does a better job. At the moment it's marked as "alpha 1" for Drupal 6, but in my experience so far it works pretty well (no bugs).
Simply install it and a 'directory' item is added to the navigation menu. The configuration is simple, you select the node types to exclude from the directory, and the vocabularies to present in the directory.
The directory page lists each of the vocabularies, then within each vocabulary the terms in the vocabulary.
It appears to override the normal taxonomy term pages and add to it the child terms. Unfortunately it doesn't show the term description.