Google Books (previously known as Google BookSearch and Google Print) is a service from Google, Inc. that searches the full text of books and magazines that Google has scanned, converted to text using optical character recognition (OCR), and stored in its digital database.
The WorldCat database is the most comprehensive bibliography, with over 179 million bibliographic records representing over 400 languages and covering over 4,000 years of knowledge. It allows you to search a combined catalog of most of the libraries in North America, and many in other parts of the world.
Library of Congress collections contain over 158 million books, periodicals, manuscripts, maps, music, recordings, images, and electronic resources. More than 18 million records describing these collections are located in the LC Online Catalog. You can search these records by keyword or browse by authors/creators, subjects, name/titles, uniform titles, and call numbers. Browse lists also include searching aids such cross-references and scope notes.
The Center for Research Libraries (CRL) is an international consortium of university, college, and independent research libraries. Founded in 1949, CRL supports original research and inspired teaching in the humanities, sciences, and social sciences by preserving and making available to scholars a wealth of rare and uncommon primary source materials from all world regions.