The first project of its kind, Project Gutenberg is the largest single collection of free online books.

A project of the Internet Archive, Open Library is a lending library of over 200,000 ebooks and a source of over 1,000,000 free ebooks.

The Electronic Text Center contains over 2,100 publicly-available ebooks from the University of Virginia Library's Etext Center, including classic British and American fiction, major authors, children's literature, American history, Shakespeare, African-American documents, the Bible, and much more. They can be read both online and with the Microsoft Reader and Palm Reader.

Founded in 1993, this website that facilitates access to books that are freely readable over the Internet

This site contains over 800 texts of classic literature, drama, and poetry together with detailed literature study guides. It also includes a large reference book and non-fiction section.

Google Books is a collection of online books. You can get the entire text of some books. For other books, you can get only part of the book, a "preview."