I've just discovered LibraryThing, while snorting my tea through my nose on account of reading too much Miss Snark. Of course, it is irresistible and amazing and I just wasted lo, these many minutes plugging books into it for the joy of cataloguing the collection and for apparently no other reason. The Victorians had nothing on us cyber-freaks with online collecting widgets, dudes. And do not ask me about my massive laboriously produced BibTeX library. No, do not. It does not have pretty pictures. I said don't ask.
Speaking of perversity, I especially like this little feature at LibraryThing: the UnSuggester. The UnSuggester considers all the books registered with LibraryThing, and given a particular title it names the books least likely to be in a library with that book.
This is utterly twisted and perverse and therefore fabulous. I tried it out three times. First, a seminal scholarly item forming the basis for all of my research. Ahem. Second, a very popular piece of fiction which I enjoyed very much. Third, a more outré piece of fiction. (None of your beeswax).
Witness my eyebrows raising. In each case, I owned at least one, and in one case four of the top ten unsuggestions for these books. That means, statistics lovers, that once the UnSuggestor had considered the 185,831 members of LibraryThing and their 12,712,806 books, it found out, basically, that I own things which no other person has on the same shelf.