Creative Commons Blog writes about Manybooks.net – a very useful website which contains over 19,000 ebooks, available for free:

With the advent of more ebook reading devices, sites like Manybooks.net are providing a useful service in transforming digital materials into a variety of electronic formats that can be read by several different ebook readers and mobile devices. All of the 19,000+ ebooks on Manybooks are available for free. Many works are originally sourced from Project Gutenberg, a longstanding project to release books in the public domain as digital texts.

At the moment, Manybooks.net hosts about 130 Creative Commons works in multiple formats.