Bartleby.com an online collection of digital reference books, poetry, fiction, and nonfiction. Includes such classics as Strunk's Elements of Style and Frazer's Golden Bough.
ManyBooks This site has close to 30,000 eBooks available for free. They also appear to support a number of devices/eReaders..
eScholarship includes digital journals, online books, conference proceedings, and working papers from scholars throughout the University of California.
Google Book Search locate books on all types of topics and new titles are being added daily. Some books are available in limited portion due to copyright or publisher restrictions and you may need to create a google account in order to view some digital book content.
Humanities Text Initiative a collection of literary, historical and religious texts developed by the University of Michigan . Includes projects like the American Verse Project and the Making of America.
Internet Public Library: E-Book Links includes a list of electronic e-books freely available through the Internet.
Online Books Page The goal of the Online Books Page is to facilitate access to books that are freely readable over the Internet. This site includes a searchable database of over 20,000 book titles available from many different sources. This index of ebooks (across multiple sites) is hosted by the University of Pennsylvania
Online Literature Library: An Online Library of Literature includes an index of thirty authors.
Project Gutenberg provides access to books in electronic text format after they entered the public domain. Includes literature and reference sources such as almanacs, encyclopedias, and dictionaries. The works may be searched or browsed by author or title.
UVa Text Collection search the University of Virginia's collection of thousands of ebooks, "including classic British and American fiction, major authors, children's literature, American history, Shakespeare, African-American documents, the Bible, and much more.