Open Access (OA) Publishing

• arXiv - Open access to 876,925 e-prints in Physics, Mathematics, Computer Science, Quantitative Biology, Quantitative Finance and Statistics (Cornell University) 
• bioRxiv - A free online archive and distribution service for unpublished preprints in the life sciences. By posting preprints on bioRxiv, authors are able to make their findings immediately available to the scientific community and receive feedback on draft manuscripts before they are submitted to journals.
• CORE is a multidisciplinary aggregator of OA research, the largest collection of OA articles available. It allows users to search more than 219 million OA articles. While most of these link to the full-text article on the original publisher's site, or to a PDF available for download, five million records are hosted directly on CORE.
• DOAJ - Open Access Journals - This service covers free, full text, quality controlled scientific and scholarly journals with the aim to cover all subjects and languages. There are now 5718 journals in the directory. 
• Digital Public Library of America (DPLA) - The Digital Public Library of America brings together the riches of America’s libraries, archives, and museums, and makes them freely available to the world. It strives to contain the full breadth of human expression, from the written word, to works of art and culture, to records of America’s heritage, to the efforts and data of science.
• EconBiz is a great resource for economic and business studies. A service of the Leibniz Information Centre for Economics, it offers access to full texts online, with the option of searching for OA material only. 
• Free Medical Journals - Unrestricted full-text access to medical journals
• INASP - International Network for the Ability of Scientific Publications. 
• JURN - A curated academic search-engine, indexing 3,670 free open access ejournals in the arts & humanities.
• OpenScience - Functioning as a research and publishing network, ScienceOpen offers OA to more than 74 million articles in all areas of science. Although you do need to register to view the full text of articles, registration is free. 
• Paperity - multidisciplinary aggregator of Open Access journals and papers.
  PLoS- Public library of science - a nonprofit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource.
• PubMed Central (PMC) -  free full-text archive of biomedical and life sciences journal literature at the U.S. National Institutes of Health's National Library of Medicine (NIH/NLM). 
• Social Science Research Network (SRRN)  - consists of two parts: an Abstract Database containing abstracts on over 508,000 scholarly working papers and forthcoming papers and an Electronic Paper Collection currently containing over 415,100 downloadable full text documents in Adobe Acrobat pdf format.

VIEW a more complete list complied by Purdue University NW Libraries 

*Many publishers now how catalogs of open access journals. This content is index in the same database as traditional journals. 

• Cambridge U Press Open Acess Books - listed together with OA journals, this collection continues to grow. 
• Directory of Open Access Books - Multi-Subject; Provides access to e-books on various subjects.
• InTech Open -  Read, share and download more than 5,900 peer-reviewed Open Access books
• JSTOR Open - More than 8,000 Open Access books from 100+ publishers, including Brill, Cornell University Press, De Gruyter, and University of California Press, are now available at no cost to libraries or users.
• MIT Press Direct to Open - use limits to see only OA titles
• National Academies Press-  the National Academies of Sciences, Engineering, and Medicine on a wide range of topics in science, engineering, and medicine on important matters in science and health policy.
• OpenAccess eBooks - Open Access eBooks is an international publisher of eBooks. 
• Open Book Publishers - leading independent open access academic press that publishes peer-reviewed monographs, edited collections, textbooks, critical translations and more.