There are an increasing number of online resources for free books, either being supplied in digital format or in the form of book swapping. Classic literature is particularly easy to obtain online due to the expiry of their copyrights but an increasing number of authors are understanding the value of the exposure gained by offering their books free of charge.
Baen Free Library - Free, modern novels contributed by the authors themselves.
Book Crossing - Leave your old books in a public place for others to pick up and find where others have left their books for you!
Book Mooch - Give books away, get books for free; free book exchange portal.
Books Online - More than 32,000 completely free downloadable books.
Classical Literature Library - 1258 classic books, both fiction and non-fiction for free download.
Darwin Online - The Complete works of Charles Darwin Online.
Dwalin - Plain text novels online.
Free Computer Books - Technical manuals on computers and programming.
FullBooks.com - Hundreds of books available to download, includes authors such as Dumas, Balzac and Nietzsche.
Google Book Search - Google has digitized many books from library collections, search for these free books here.
Great Books Index - From Darwin to Jane Austin, from Dickens to Marx, there is a huge list of downloadable books for free.
Modern English Collection - Fiction, non-fiction, poetry, drama, letters, newspapers, manuscripts and illustrations from 1500 to the present from the University of Virginia.
Online Books Page - University of Pennsylvania lists over 25,000 free books for downloading.
Paperback Swap - Swap books with other users.
Project Gutenberg - Popular books from the oldest provider of free downloadable books on the Internet.
S F Books - Online Sci-Fi book swapping club.
The Literature Network - The full text of 1000s of classic stories, poem and essays for free.
Wiki Books - Free textbooks on a number of subjects.
Woodland Forest Chronicles - Two free mini adventure gamebooks; "The Wounded Falcon" and "The Lost Diary".
Wowio - Free books including comic books.