Books may be available at no cost in electronic form if they are out of copyright (hence in the Public Domain), or if they are published under a Free license, such as GFDL or Creative Commons. The OLPC project is critically dependent on availability of Free books on every subject. We need to talk to many textbook publishers about Creative Commons--Developing Countries licenses for their books.
Here are some sources.
- Project Gutenberg publishes mostly English material, nearly all in the Public Domain. (Some works copyrighted but freely distributable--not necessarily Free. For instance, Cory Doctorow's works are CC-NC-ND.)
- McMaster University Archive for the History of Economic Thought
- The Perseus Digital Library Classics in original languages and English translations, and more.
- The Internet Archive More than 300.000 books, principally from American and Canadian libraries. In PDF and djvu format.