Tag pages
Each tag’s page (example) displays pages sorted by the number of other tags they have in common. In a sense, it’s not showing a list of pages that have the tag. It’s showing a list of tags that are related to the current tag, along with the pages that represent that relation. I think that’s a lot more interesting.
I think it would be neat to have some way to explore tags and their relations, but I’m still thinking about the best way to realize that.