I've been a Project Gutenberg fan, http://www.gutenberg.org/wiki/Main_Page, for 10+ years. I even read books at work, during downtimes, or during lunch. I felt like such a cheater, reading Pride and Prejudice while getting a paycheck!
The creator of Project Gutenberg is the inventor of the Ebook (he started way back in 1971). The site has over 100,000 free books available for download.
They also need volunteers to record audio books, so if this strikes your fancy, sign on and help them out!