Amazon.com - Search one million titles. It is a great place to locate hard-to-find titles which are in print. You can even find used books. You can search by author, title, subject and keyword. Includes lists from the New York Times Book Review and titles in the news.
Barnes and Noble - Search for music, movies, gifts and books online. They also provide book recommendations, reviews, and the latest arrivals.
Islamic Bookstore - The Internet's Largest Islamic Store.