Hey! Did you get a new E-Book Reader for the Holidays? While e-books are cheaper than regular books, free is even better. If you're not looking for something on the New York Times Bestseller List, you should be able to find some great books to download here.
The first place to look is in the free ebook collection on Amazon.com. There you will find titles (some promotional, some public domain) made free by Amazon as well as links to Project Gutenberg, Open Library, Many Books, and the Internet Archive. All four of those places offer free downloads.
Some other places where you can find free ebooks are the Google eBookstore and Feed Books.