- Project Gutenbrg -
Project Gutenberg is an vast online library full of books that are in the public domain and can be downloaded for free in various formats including plain text, html, pdf, mp3, postscript, and various other formats. You'll find classics like Dracula, Moby Dick, and The Art of War, but also several recent books that the author chose to release.

- The Internet Public Library -
This site is a human archived repository containing links to thousands of web pages that contain free online books.

- The Online Books Page -
This site works along the same lines as The Internet Public Library where it is hand archived and links to various web pages all over the Internet.

- Abe Books -
This is a great site to purchase used books. It has a huge inventory of various stores all across the world. The books are searchable by author, title, keyword, ISBN, publisher, book style, pricing, publish year, and many other features.

- The Baen Library -
Many of Baen's science fiction authors have placed their books online free of charge to be read and downloaded.

- Free Books For Doctors -
Links you to many other web pages that contain the contents of public domain medical books.

- Project Aon -
Project Aon is dedicated to converting the complete Lone Wolf book series to an online HTML format so everyone can read the books for free.

- The Kai Monastery -
The most complete fan site dedicated to the Lone Wolf book series by Joe Denver.

- Amazon -
Amazon is on online store for books and many other forms of media. Their prices are reasonable.