Podfeed is a podcast directory.
It uses a single level hierarchy of topic categories, plus each show has tags associated with it for a secondary topic index.
The show listing has a description, link to the home page, and some other data. It lists items from the show, along with the description of each item. There is a media player along with each listing.
Users can register, they can rate shows, create a custom "podfeed", etc. To add a podcast to the site requires being registered.
The site is pretty well done.