There are plenty of free audiobooks you can get from audible and audiobooks.com!
Check out the link here! www.openculture.com/freeaudiobooks
There are plenty of free classics here as well for those who are interested!
For just plain ebooks, a great place is Project Gutenberg! http://www.gutenberg.org/
Another great place is wikibooks, although wikibooks is more educational in my opinion, and it's written by community authors. https://www.wikibooks.org/