Here is a sampling of websites where you can find full textbooks online.
Project Gutenburg has many of the great classic authors and works available, including Chaucer and Shakespeare.
Bartleby.com is a good resource for free eBooks on lots of topics and genres.
Bibliomania Over 2000 digitized books.
Bible Gateway: Taking a religion class and need to find a passage from the Bible? You can select which version you want and search for the quote or chapterand verse. Need a commentary, concordance or bible dictionary? Try Crosswalk, which has Strong's Concordance, the Geneva study Bible, and John Wesley's commentary as well as many other resources.
Classic Reader: Read, search and annotate great works of literature. New works are added regularly.
Directory of Open Access Books (DOAB): 71,000 academic peer-reviewed ebooks from 122 publishers.
ICDL: The International Childrens Digital Library - If you need to find a multicultural children's book or are interested in children's books from other countries, this site has many interesting selections.
National Academic Press has 2,500 free eBooks for use and many more print books for purchase.
Oxford Journals: Open Access Books.funded by JISC Collections and the Arts and Humanities Research Council (AHRC).
University of Pennsylvania: Listing of places to find books online.
University of Virginia Library: Contains the writings of Thomas Jefferson, Frederick Douglas, and other men and women who helped in shaping America, as well as children's literature and other works of fiction and non-fiction.
Psych Classics: Full texts of a large number of historically significant public domain documents. You can find works by Maslow, Dewey, Freud, Lovelace, Thorndike, and more.
Looking for that elusive yet famous quote? Try searching Bartlett's Familiar Quotations
MP3 Books: Free Audio Books in MP3 Format
Presidential Speeches: The MSU Vincent Voice Library is working to preserve over 100 years of historical spoken word recordings like those of the U.S. Presidents and is pleased to share these sound samples from its collection.
Library of Congress: Audio recordings of books, speeches, and music files.