I think a tag cloud would be a great idea!
I can't count the number of times I've sifted through all the pages returned by super search, looking for very specific topics. I add my favorite threads to my scratch pad, and then try to organize them later. I know many monks do the same, so there's already a personal effort at tagging going on.
The store of knowledge here on PM is vast, and it should be a goal of this site to make it easy for people new to perl to be able discover topics which they didn't even think of searching for.