Thanks for the site :)
It might be a good idea to move to Drupal 6 as soon as possible, before you depend on too many Drupal 5 only modules. Clean URLs would be nice.
Most important (for me) is to have OpenID login. It's standard in Drupal 6 and comes as a 3rd party module for Drupal 5.
Other than that, I haven't spent much time around yet. Perhaps setup some kind of wiki features to let anyone edit a class of pages.