In Drupal, you can provide a description for each term in a taxonomy vocabulary. The default taxonomy term pages of Drupal 6 include the description at the top of each page (if only one term is present).
Recently I have upgraded a customer site from Drupal 5 to Drupal 6. The site contains a number of custom modules that required considerable work because of some changes in the Drupal API.
There is an interesting presentation by psychologist Barry Schwartz at TED called "The paradox of choice". He explains why people are not better off when there is too much choice.