Project Gutenberg
http://www.gutenberg.net/
Project Gutenberg is the brainchild of Michael Hart, who in 1971 decided that it would be a really good idea if lots of famous and important texts were freely available to everyone in the world.

Bibliomania
http://www.bibliomania.com/bibliomania-static/index.html
Free Online Literature with more than 2000 Classic Texts.

The Internet Archive
http://www.archive.org/texts/bookmobile-books.php
The Internet Archive is a 501(c)(3) public nonprofit that was founded to build an ‘Internet library,’ with the purpose of offering permanent access for researchers, historians, and scholars to historical collections that exist in digital format.