www.goodreads.com It's a social cataloguing site for books. I love it, I've found 75% of the books I've read in the past two years through their database. It also helps me to have a list of books "to-read" available online, so I can add to it, and easily request stuff through local libraries and such. And it's free, unlike other similar services I've seen. My Goodreads profile. Let's be friends and share books and junk!