Great thread.
Here's an amazingly comprehensive site:
The Internet Sacred Text Archive:
Internet Sacred Text Archive Home
"Welcome to the largest freely available archive of online books about religion, mythology, folklore and the esoteric on the Internet. The site is dedicated to religious tolerance and scholarship, and has the largest readership of any similar site on the web."
They include not only esoteric stuff, but mainstream classics like "Think and Grow Rich" and many more. Poke around--you'll be amazed.