Library Thing is pretty cool. I added about 15 books Ihave recently read to my bookshelf. It was interesting to see that some of my books were on LOTS of other folks bookshelves, and some of my books were only on a few peoples' shelves. I shall go back and add tags to my books (I guess that would be the cataloging aspect - duh) It will be easier after looking at tags that other folks used for my books.
I also like the suggestions for books to read based on what I have been reading. This could be great for those kids who "want another book like Harry Potter, or Hatchet," etc.
I would LOVE to put all my personal library books in Library Thing!