Index your books on WorldCat!

Enter the title of an item from your collection in the box at the left. Start a list of your books. Add notes. I add one or more per visit to my list from the random titles that come up in the LibraryThing widget. My list-in-progress is public.
Registration is free. Take a moment to create an account, and you’ll be able to:
1. Create a profile
2. Build and maintain public and private lists of books owned by libraries
3. Add your notes, rating and reviews of the items.
You are allowed multiple lists: Things I own, Things I recommend, topical or want lists.
You may then sort your list by author, title or date, and export or print your lists in a variety of formats. Exports may be in HTML, Rich Text, or RIS, and for citation style, you may chose APA, Chicago, Harvard, MLA or Turabian.

The fun part is seeing which libraries own copies of your books – in your area, across the country and internationally. You may find one library-owned copy, or one hundred.
The weakness is that if you can not find the book in any library, they do not provide a way to add it to your list yourself. Also, some items in WorldCat have images, but many do not. For images and unique items, LibraryThing is the answer.