Directory of Open Access Journals
A multidisciplinary, community-curated directory, the Directory of Open Access Journals (DOAJ) gives researchers access to high-quality, peer-reviewed journals. It has archived more than two million articles from 9,519 journals, allowing you to either browse by subject or search by keyword.
Directory of Open Access Books
Open Access Repositories
OpenDOAR, or the Directory of Open Access Repositories, is a comprehensive resource for finding open access journals and articles. Using Google Custom Search, OpenDOAR combs through open access repositories around the world and returns relevant research in all disciplines.
Run by Indiana University, the Digital Library of the Commons (DLC) Repository is a multidisciplinary journal repository that allows users to check thousands of free and open access articles from around the world. You can browse by document type, date, author, title, and more or search for keywords relevant to your topic.
The CIA World Factbook is a little different from the other resources on this list in that it is not an online journal directory or repository. It is, however, a highly useful research database for academics in a variety of disciplines. All the information is free to access, and it provides facts about every country in the world, including information about history, geography, transportation, and much more.
Dryad is a digital repository of curated, open access scientific research. It is run by a not-for-profit membership organization that aims to "promote a world where research data is openly available, integrated with the scholarly literature, and routinely reused to create knowledge." It is free to access, but note that there is a publishing charge associated if you wish to publish your data in Dryad.
Taking its name from Zenodotus, the first librarian of the ancient library of Alexandria, Zenodo is a tool that was "built and developed by researchers, to ensure that everyone can join in open science." You can sort by keyword, title, journal, and more and download open access documents directly from the site.
The dblp Computer Science Bibliography is an online index of major computer science publications. Although it provides access to both free access articles and those behind a paywall, you can limit your search to only full-text articles. The site indexes more than three million publications, making it an invaluable resource in the world of computer science.