Has anyone seen the new IMDB MoKA system? You can give it a list of keywords and it will give you the set consisting of the intersection of those keywords, as they apply to IMDB movies. For instance, if you search for zombie/car-accident/chainsaw, it will give you all (both) movies in their index that have been tagged with all three keywords. I would love a plugin to do this on my own site. Someone could engineer a URI like http://www.mcgees.org/category/radio/politics/, and it would return all (both) posts that have been tagged radio and politics.