BookServer
A project of the Internet Archive, BookServer collects information on digital books that are available online, either free or for a fee.

The Online Books Page
From the University of Pennsylvania Library, this "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."

Bartleby
"The concluding line of Herman Melville’s classic American short story Bartleby, the Scrivener reads: 'Ah Bartleby, Ah Humanity!' And so, Bartleby.com—after the humble character of its namesake scrivener, or copyist—publishes the classics of literature, nonfiction, and reference free of charge for the home, classroom, and desktop of each and every Internet participant."

Google Book Search
When you choose Full View -- "If  [Google has] determined that a book is out of copyright, or the publisher or rightsholder has given [them] permission, you'll be able to page through the entire book from start to finish, as many times as you like. If the book is in the public domain, you'll also be able download, save and print a PDF version to read at your own pace."

Project Gutenberg
"The Project Gutenberg Philosophy is to make information, books and other materials available to the general public in forms a vast majority of the computers, programs and people can easily read, use, quote, and search." There are three portions of the Project Gutenberg Library:

• Light Literature; such as Alice in Wonderland, Through the Looking-Glass, Peter Pan, Aesop's Fables, etc.
• Heavy Literature; such as the Bible or other religious documents, Shakespeare, Moby Dick, Paradise Lost, etc.
• References; such as Roget's Thesaurus, almanacs, and a set of encyclopedia, dictionaries, etc.
  

Gale Virtual Reference Library
The full text of the following reference books:

• Beacham's guide to the endangered species of North America, 6v, 2000.
• Biology, 4v, 2002.
• Encyclopedia of espionage, intelligence, and security, 3v, 2004.
• Encyclopedia of population, 2v, 2003.
• Encyclopedia of small business, 2nd edition, 2v, 2002.
• Fashion, costume, and culture: clothing, headwear, body decorations, and footwear through the ages, 5v, 2004.
• Gale encyclopedia of alternative medicine, 2nd edition, 4v, 2005.
• Gale encyclopedia of cancer, 2nd edition, 2v, 2006.
• Gale encyclopedia of genetic disorders, 2nd edition, 2v, 2005.
• Gale encyclopedia of medicine, 3rd edition, 5v, 2006.
• Gale encyclopedia of multicultural America, 2nd edition, 3v, 2000.
• Gale encyclopedia of U.S. economic history, 2v, 1999.
• Renaissance: an encyclopedia for students, 4v, 2004.
• St. James encyclopedia of popular culture, 5v, 2000.
• U*X*L encyclopedia of landforms and other geologic features, 3v, 2004.
• World of earth science, 2v, 2003.