The Directory of Open Access Journals (DOAJ) is a very comprehensive list of journals that publish only open access content. Note, however, that publishers must submit information on their journals to DOAJ, so it is not absolutely complete. DOAJ records include the publisher, language of publication, start date and whether or not there is a publication fee for authors, with a link to the journal’s instructions for authors where available.  Some journals have allowed DOAJ to directly display the journal’s table of contents information as well.

The Digital Commons Network brings together scholarship from hundreds of universities and colleges, providing open access to peer-reviewed journal articles, book chapters, dissertations, working papers, conference proceedings, and other original scholarly work. This constantly growing body of publications is curated by university librarians and their supporting institutions, and represents thousands of disciplines and subject areas.

Elsevier hosts a small number of delayed open access journals.  Currently all open their content to non-subscribers 12 months after initial publication.

Highwire Press, operated by Stanford University, publishes a large number of journals for scholarly societies.  The page above lists the journals with free content, and specifies the period for each journal after which back issues become open access.

• BioMed Central – contains biomedicine journals. There are broad interest titles and specialist journals in biology and medicine.
• Free Medical Journals – provides scholarly full-text journals focusing on nursing, allied health fields, and many medical disciplines.
• Public Library of Science (PLoS) – an online database of biomedical journal citations and abstracts covering all areas of medicine and indexed with NLM's controlled vocabulary, the Medical Subject Headings (MeSH®). Full text must be ordered from another library using the Interlibrary Loan Article Request Form. The monthly PLoS Biology, was first issued online in October 2003 by the Public Library of Science (PLoS), a nonprofit organization of scientists and physicians. 
• Wiley Open Access Journals – browse journals by Discipline – Health Sciences has full-text articles. 
• World Bank Data – includes World Development Indicators (WDI); Global Development Finance (GDF); Africa Development Indicators (ADI); and Global Economic Monitor (GEM).

• arXiv.org – Physics, Mathematics, Computer Science, Quantitative Biology, and Quantitative Finance and Statistics subject search and browse drop down menu available.
• ChemistryCentral – covers organic chemistry extensively. Other free titles listed by Springer.
• E-Print Network–Energy, Science, Technology for the Research Community – Resources from the United States Department of Energy (DOE) Office of Science
• Hindawi Publishing Open –Access Journals – covers all areas of Science, Technology, Medicine and some Social Sciences.
• Institute of Electrical and Electronics Engineers (IEEE) Open-Access – groundbreaking research and applications-oriented articles; contains hybrid journals, fully-open topical journals and multidisciplinary Mega Journal.
• The Institution of Engineering and Technology (IET) Open-access Journal – fields include Electrical and Electronic engineering, Mechanical engineering, Energy engineering, Civil engineering, Micro- and Nanotechnology, Computing and Software, Biomedical engineering and Materials engineering. 
• Open Access Journals Search Engine (OAJSE) – service covers free, full text, quality controlled journals. We aim to cover journals in all subjects that are published in English language. There are now 4,775 journals in the directory. All are searchable at article level.

• Creative Commons – a nonprofit organization that enables the sharing and use of knowledge and provides copyright licenses that act along with the legal rights of copyright laws.
• Google Scholar – search for academic literature on many subjects and use Google Scholar Search Tips
• Open-Access initiative (OAI) OAISTER – connecting you to libraries worldwide with open access.
• Open Access Scholarly Publishers Association –  represents the interests of Open Access (OA) journal publishers globally in all scientific, technical and scholarly disciplines. 
• Open Knowledge Foundation  – promotes “meetups” and initiatives for positive change to cultures, policies and business models at large organizations to make opening up information acceptable and desirable.
• Registry of Open Access Repositories  – promotes the development of open access by providing timely information about the growth and status of repositories throughout the world.

While Open Access publishing has advantages for scholarly communities, the model also presents opportunities for exploitation and deceit. Organizations claiming to run peer-reviewed, open access publications are sometimes fronts operated to collect production fees from authors (APCs), publishing work with little or no review. Additionally, there is debate around what constitutes a predatory journal, and this lends an element of subjectivity to their classification. The links below are good resources but should not be considered authoritative. When consulting them, it is important to complement their information with your own scrutiny. For assistance with this, contact the subject specialist librarians for your academic field

How to Avoid Predatory Journals -- a Five-Point Plan by Jocalyn Clark. The BMJ (January 19, 2015)

Predatory Journals: What they are and how to avoid them by Susan A. Elmore and Eleanor H. Weston. Toxicologic Pathology (April 22, 2020)