* The Internet Archive: Founded in 1996, the Internet Archive is a non-profit organization that has digitized millions of books, movies, music, and other cultural artifacts. Their "Open Library" project specifically focuses on digitizing books.
* Google Books: Google launched their Google Books project in 2004, aiming to digitize millions of books from libraries and publishers. While controversial due to copyright issues, it significantly contributed to the availability of digitized books.
* Project Gutenberg: Founded in 1971, Project Gutenberg is a volunteer-driven project focusing on creating and distributing ebooks of public domain works. While not as large-scale as the other initiatives, it played a significant role in popularizing ebooks and establishing a model for free digital books.
* National Libraries: Many national libraries, such as the Library of Congress and the British Library, have been actively digitizing their collections for research and preservation purposes.
In summary, the massive digitization of books can be attributed to a collaborative effort involving non-profits, technology companies, and institutions like national libraries. These initiatives have created vast digital libraries, making information more accessible and preserving cultural heritage for future generations.