From now through August 4, you have access to over two million free eBooks through a project called The World eBook Fair. The project is a cooperative effort of various organizations and programs focused on collecting and making available open source and public domain eBooks (Alphabetical list of eDocument collections.) Many of the books are available free throughout the year, but at least 500,000 are typically only avaiiable through the World Public Library, which has a small annual fee of $8.95.
The project, in its third year, was co-founded by Michael Hart, founder of Project Gutenberg.
Note: You don’t need to have a Kindle or other brand of eBook reader to read an eBook (although these free books work on those devices) — nearly all of these books are available in both text and PDF versions and many are available in a format specifically designed for smart phones. Lots of open source audio books and music are also available.