The term open access refers to the free and unrestricted online availability of journal literature.
Specific features of open access are clarified in various public statements, including the Budapest Open Access Initiative, the Bethesda Statement on Open Access Publishing, and the Berlin Declaration on Open Access.
Peter Suber's Open Access Overview provides good background information.
For help evaluating open access journals consult the Open Access Journal Quality Indicators.
For a complete list of subject specific open access repositories, check Open DOAR.
|AgEcon||Agricultural and applied economics.||A free, open access repository of full-text scholarly literature including working papers, conference papers, and journal articles.|
|arXiv||Computer science, mathematics, physics, quantitative biology, finance, and statistics.||Repository of electronic preprints (known as e-prints) approved for publication after moderation.|
|bioRxiv||Life sciences.||Pronounced bio-archive, bioRxiv is a free online archive and distribution service for unpublished preprints.|
|Cogprints||Psychology, neuroscience, and linguistics, and many areas of computer science, philosophy, biology, medicine, anthropology, and any other portions of the physical, social and mathematical sciences that focus on the study of cognition.||
Repository for self-archive papers.
|PubMed Central||Biomedical and life sciences.||Free archive of biomedical and life sciences journal literature at the U.S. National Institutes of Health's National Library of Medicine (NIH/NLM).|
|RePEc||Economics.||Not a repository in the strict sense of the word, but rather a decentralized bibliographic database with links to full texts. About half of the 1.5 million publications are freely accessible.|
|Social sciences.||Open archive of social science research.|
|SSRN||Economics and business studies||Social Science Research Network is the largest disciplinary repository of publications.|