More specifically, does anyone have any recommendations for best in class sites that publish large amounts of content in a taxonomy structure. That is, where pages roll up to/from categories, sub-categories, and even sub-sub categories.

Our site has 19 categories, hundreds of sub categories, and tens to hundreds of thousands of pages of content.

I want to find the best way for users and search spiders to find our content, especially the deeper level content.

Would love your opinions/recommendations. Thanks!

Kristen