Manuals - Gutenberg Project

Project Gutenberg offers over 50,000 free ebooks: choose among free epub books, free kindle books, download them or read them online.

They carry high quality ebooks: Their ebooks were previously published by bona fide publishers. They digitized and diligently proofread them with the help of thousands of volunteers.
No fee or registration is required.

http://www.gutenberg.org/wiki/Main_Page