Just completed a really satisfying addition to the Ultralab web site. I have redesigned the footer to be a dynamic list of the keywords used to label content in the web site. The keywords also link to searches based on these keywords. As people add new keywords these will be automatically added to the footer. As they label material, new or old, it can be found through the footer keyword searches.
All this is easy because of the neat Python functions for mapping lists, converting to strings and the level of introspection that object-oriented database-driven systems like Plone (and Zope) offer.