Project Gutenberg has been around for along time, relatively speaking. They still have lots of great books online, totally free (as in free of charge and you are free to do what you want with them), and continually being updated. The new ebook sites are all fine and good, but this classic site is full of ..um…classics! And much more. You deserve to pop in and take a browse.
Smart People I Know 
I saved literally hundreds of dollars in college printing things out from Project Gutenberg instead of buying the Penguin Classics edition of thousand year old philosophy texts.