Emma's post and Tom's response are certainly helping with that. I fully agree that although user tagging can't replace an authoritative catalogue, it does facilitate browsing using everyday language and we should be looking at ways to integrate them with the catalogue.
Tag clouds can be a nice way to browse blogs especially, so I thought I'd share what the one on my blog looks like so far. It does look much more interesting now that I've added extra tags to all my #cam23 posts.
I recommend checking out Isla's tagging system and resulting #regionaltagging discussion on Twitter.