I love LibraryThing for cataloging my books and being able to sort not only by genre and author (so straightforward!), but also by location (took place in India? San Francisco?) and themes (immigration? high school?) ... this makes it so much easier to put my fingers on a specific piece of fiction that I may have read ages ago! I do use tags, and agree that they should have "universal" appeal ("to be read" and "not owned" don't help me select a book).

Happy Reading!
Dawn
http://www.sheIsTooFondOfBooks.wordpress.com