LibraryThing - A home for your books.
Delicious Library - Delicious Library 3: Catalog your books, movies, music, software, toys, tools, electronics, & video games. Archive your life.
Openreads - An Android app for keeping tracks of books you have read. - GitHub - mateusz-bak/openreads-android: An Android app for keeping tracks of books you have read.
Goodreads - See what your friends are reading.
Book Catalogue - This is a simple book catalogue application, to store a list of your books.
Bookshelf - Your virtual library - Organize your home library books on multiple virtual bookshelves.