LibraryThing
Launched in 2005, LibraryThing is a a full-powered social cataloging platform cataloging and sharing bibliographic data and building library collections. It has more than 1,500,000 users and over 70 million books. As a large book club, LibraryThing builds its catalog using Amazon, the Library of Congress and over 700 libraries around the world, including the Library of Congress. It helps users find new books or connect with other people with similar tastes.