LibraryThing - A home for your books.
Goodreads - See what your friends are reading.
Delicious Library - Delicious Library 3: Catalog your books, movies, music, software, toys, tools, electronics, & video games. Archive your life.
GoodBooks.io - Largest curated collection of 8,500+ book recommendations.
Bookicious - Find the best new book to read with books collections for makers, founders and entrepreneurs.
Bookshelf - Your virtual library - Organize your home library books on multiple virtual bookshelves.