" Abebooks is the world’s largest online marketplace for used, rare, and out-of-print books. Abebooks connects those who buy books with those who sell books, providing abundant selection at affordable prices.
Bookbuyers love the variety and selection of 40 million books, offered by 10,000 booksellers who list on Abebooks. Readers find bestsellers, collectors find rare antiquarian books, students find textbooks, and treasure hunters find books they’ve been seeking forever. Booksellers love Abebooks for providing the tools to help them succeed online and dedicated customer support. Every day, thousands of people find the right book at the right price on Abebooks.
Abebooks is a global company with sites dedicated to bookbuyers in North America (Abebooks.com), France (Abebooks.fr), Germany (Abebooks.de), and the UK (Abebooks.co.uk). These domestic sites serve specific countries while making unique book inventories available to all. Through strategic partnerships with Amazon, Barnes & Noble, and eBay/Half.com, Abebooks has become the most important virtual supplier of used books while expanding selling avenues for booksellers." ... more on Abebooks

" The Online Books Page is a website that facilitates access to books that are freely readable over the Internet. It also aims to encourage the development of such online books, for the benefit and edification of all.
Major parts of the site include:
An index of thousands of online books freely readable on the Internet
Pointers to significant directories and archives of online texts
Special exhibits of particularly interesting classes of online books
Information on how readers can help support the growth of online books" ... more

Catholic Online

" Catholic Online, located at www.catholic.org, gives the largest and broadest population of Catholics worldwide easy access to comprehensive, educational and timely information about Catholicism, and provides a range of easy methods to integrate their faith into their daily lives. The mission of Catholic Online (COL) is to accurately represent the Catholic religion: its’ “past” and present. Today, Catholic Online provides over five million pages of content including the largest online historical and biblical database about the Catholic Church including comprehensive information about over 7,000 Catholic saints and comprehensive online scriptures from all books of the Old and New Testament.
Catholic Online reaches a highly targeted audience of over to 100 thousand Catholic users per day and up to 10 million page impressions per day and 50M hits. Visitors come from over 120 countries around the world. Over 100,000 users take advantage of free email accounts and access COL every day!
Catholic Online has consistently provided the world wide Catholic Community with dependable and reliable content and Internet services for over 10 years. We have the largest Catholic Online presence on the Internet. In order to continue to build OUR Catholic Online Community your active support is needed. " more

The History of Christianbook.com

" Christianbook.com is the online home of Christian Book Distributors, a company that started long before the World Wide Web had even begun to take its shape. The company began as a small family affair when, in 1978, the elder of two brothers decided to start a mail-order business to earn a little extra money while attending Bible college. At first, CBD carried only a few academic titles and offered them at discounted prices to students. However, with the help of their father (a pastor) and mother, the two brothers soon watched their business take off. Orders poured in and the driveway, bedrooms, and garage of their small house overflowed with boxes and boxes of books... " more

" BookFinder.com, the open marketplace for books online, is produced by 13th Generation Media, based in Berkeley, California. The company was founded by a couple of recent University of California grads with a taste for grassroots-driven ecommerce, and afflicted with severe cases of bibliophilia. BookFinder.com's goal is to provide fellow readers unbiased real-time information about books available online.
Rather than selling books ourselves, our team of high-tech book geeks has worked to create a truly useful free book search tool for all kinds of readers. BookFinder.com is a one-stop search site that lets users view the collections of over 40,000 sellers of new, used, rare, and out of print books. The forty million titles available constitute the largest book catalog available anywhere, either online or offline.
BookFinder.com was first developed in 1996 by then-19-year-old UC Berkeley undergraduate Anirvan Chatterjee [offsite link]. Over the years, the site has grown to become one of the best online resources for book related ecommerce, as evidenced by the great feedback we've received from our users and the press. "

" Alibris connects people who love books, music and movies to thousands of independent sellers around the world. Our proprietary technology and advanced logistics allow us to offer over 30 million used, new and hard-to-find titles to consumers, libraries and other institutions. "