DOAJ

arXiv is the open-access preprint repository where physicists, mathematicians, and computer scientists publish research papers freely, often months or years before journal publication. It lets anyone read frontier research, including most AI papers, without paywalls or institutional access. Preprints are not always peer reviewed, so reading critically is part of the deal.

The Internet Archive is a nonprofit library preserving the web through the Wayback Machine alongside millions of books, recordings, films, and software programs, all freely accessible. It is civilization's working memory against link rot and platform deletion. It is also a single organization facing lawsuits and outages, so treat it as a resource, not a backup.

OpenStax, based at Rice University, publishes peer-reviewed, openly licensed college textbooks in math, science, economics, and humanities, free to read online or download as PDF. It removes the textbook-pricing gatekeeper from self-education, and open licenses mean the books can be copied and kept forever. Coverage centers on standard introductory courses.

Project Gutenberg is a volunteer-run digital library of more than seventy thousand public-domain books, free to download in open formats with no account, DRM, or tracking. Downloaded books are permanently yours, immune to the remote deletion and license revocation that plague commercial ebook stores. The catalog skews older since it depends on copyright expiry.