Michael Webb has recently posted an article on LibraryThing. I have also recently signed up for this service and catalogues about 100 of my (many!) books. The interface is very slick, and I particularly appreciate its thriving community, as can be seen by the statistics page.
Initially I started to use it to catalogue my novels. However it has occurred to me that this might be a useful service for cataloguing books in small departments (like UKOLN, perhaps). This might provide a simple way of getting departments started in exploring use of a Web 2.0 service. And, if you are worried about potential loss of your data, there is an export function.