There are many types of open access, perhaps because it is such a young movement that it's still developing standards. That said, there are three basic types:

• Green – refers to self-archiving generally of the pre or post-print in repositories
• Gold – refers to articles in fully accessible open access journals
• Hybrid – some times called Paid Open Access, refers to subscription journals with open access to individual articles usually when a fee is paid to the publisher or journal by the author, the author's organization, or the research funder. Some of the fees are quite expensive, up to $5000. Some universities or libraries have a pool of funding available for hybrid journal publications or sometimes funding is written into grant applications for open access in hybrid journals, though these are not common instances. Some examples of hybrid open access are: iOpenAccess by Taylor Francis, Online Open by Wiley, or Sage Open by Sage. For a full list visit Publishers with Paid Options for Open Access from SHERPA/RoMEO.

Though green open access generally refers to the post-print of an article, there are three basic version types that can be self archived in repositories:

• Pre-Prints – The author's copy of article before it’s been reviewed by the publisher, or pre-reviewed
• Post-Prints – The author's copy of article after it’s been reviewed and corrected, but before the publisher has formatted it for publication, or post-reviewed.
• Publisher’s Version – The version that is formatted and appears in print or online.

If authors have signed a Copyright Transfer Agreement (CTA), publisher's policy will determine which version of an article can be archived in a repository. Most publishers allow some sort of green open access. Authors can check their CTA for this information. SHERPA/RoMEO is a database of publisher copyright policies and self archiving information that authors can use to check which version they may be allowed to archive. Not all journals are in SHERPA/RoMEO and it isn't always current, so authors may also want to check the publisher's website as well.

SHERPA/RoMEO classifies publishers into colors for easy identification:

• Green - refers to publishers whose policies allow archiving of pre-print and post-print or publisher's version/PDF
• Blue - refers to publishers whose policies allow archiving of post-print or publisher's version/PDF
• Yellow - refers to publishers whose policies allow archiving of pre-print
• White - refers to publishers whose policies do not formally support archiving any version

Source: Open Access: Types of OA

There are many discipline-specific as well as multi-disciplinary open access journals. Choose journals for publication carefully.

• ACS Open Access

Learn about the five main components of the ACS Open Access Initiatives. Publish open access with a full menu of options from ACS, including CC-BY.  ACS AuthorChoice, ACS Editors' Choice, ACS Author Rewards,  ACS Central Science and ACS Omega.  

• BioMed Central

BioMed Central Ltd., an independent publisher in London, England, provides free access to biomedical research publications. These publications include biology and medicine journal articles, current reports, and meeting abstracts. BioMed Central offers information about current controlled trials, as well as topics in modern biology.

• Directory of Open Access Journals (DOAJ)

This is a searchable directory of open access journals across all disciplines.

• Elsevier's OA Journals

Elsevier publishes many journals and scholarly works in various disciplines. This site provides a list of this publisher's open access journals.

• International Association for Media and Communication Research OA journal list

This website lists open access journals in the field of media and communications research.

• Knowledge Unlatched

Knowledge Unlatched works with libraries and academic publishers to make selected books openly accessible. The model depends on libraries contributing to cover a publisher's costs on a book; when the cost-recovery goal is met, the book becomes open access. Knowledge Unlatched encourages authors to discuss this option with their publishers. See "How can I get my book published through Knowledge Unlatched?"

• MLA Commons

A network linking members of the Modern Language Association. "MLA Commons, in addition to supporting a wide range of informal blogs and discussion groups, offers a robust platform for more formal publications—both member-generated and those initiated by the association." See also "Developing New Book Projects on MLA Commons."

• MediaCommons Press

An "in-development feature of MediaCommons promoting the digital publication of texts in the field of media studies, ranging from article- to monograph-length.”

• Open Humanities Press

An "international, scholar-led open access publishing collective whose mission is to make leading works of contemporary critical thought available worldwide." The OHP network includes several openly accessible book series published by MPublishing at the University of Michigan, as well as a selective list of autonomously-produced open access journals in critical and cultural theory.

• Open Library of Humanities

A high-profile initiative to establish a non-profit open access publisher for the humanities and social sciences. See this April 2014 CHE interview with Martin Paul Eve, Lecturer in English at the University of Lincoln, UK and co-founder of the Open Library of Humanities.

• PeerJ

An off-shoot of PLoS, PeerJ is a new open access journal in the biological and medical sciences. PeerJ operates under a unique publishing fee model, which includes lifetime membership options.

• Public Library of Science (PLoS)

PLoS publishes several well-established open access, peer-reviewed journals covering an array of disciplines in the sciences including PLOS Biology, PLOS One, and PLOS Pathogens.

• Royal Society Open Science

From the Royal Society publishing groups comes this new open access, peer-reviewed journal publishing across the range of science and mathematics.

• SpringerOpen

This is a list of open access journals published by Springer covering numerous disciplines and subject areas.

• Taylor & Francis OA Journals

Taylor & Francis publishes many journals and scholarly works in various disciplines. This site provides a list of this publisher's open access journals.

• Wiley Open Access

Wiley publishes many journals and scholarly works in various disciplines. This site provides a list of this publisher's open access journals.

List of Predatory Journals

This is a list of possibly Predatory Journals. The kernel for this list was extracted from the archive of Beall’s list at web.archive.org and the updated list at BEALL'S LIST OF PREDATORY JOURNALS AND PUBLISHERS. It will be updated as new information or suggested edits are submitted or found by the maintainers of this site.

Journals that publish work without proper peer review and which charge scholars sometimes huge fees to submit should not be allowed to share space with legitimate journals and publishers, whether open access or not. These journals and publishers cheapen intellectual work by misleading scholars, preying particularly early career researchers trying to gain an edge. The credibility of scholars duped into publishing in these journals can be seriously damaged by doing so. It is important that as a scholarly community we help to protect each other from being taken advantage of in this way.

See: Basic Criteria

One example:

InTech Open Access Publisher – Mirror site

In 2015, Thomson Reuters started indexing InTech open access books in its ISI Web of Science Book Citation Index (BKCI). BKCI is a part of Web of Science Core Collection (WoSCC) together with SCI Expanded, SSCI, AHCI and other databases. Intech Open Access Publisher appears on the list of Predatory Journals.

How to Protect Yourself from Predatory Publishers and Other Open Access FAQs

Although open access has its bad players and opportunists, the quality indicators you would look for in a traditional journal also apply to open access publishing. Keeping an eye out for these will keep you safe in your publishing journey. Look for reputable publishers, clearly stated peer review and ethical policies, transparent peer review, and a reputable (and verifiable) editorial board. Check well-known indexing services and follow their links to journal websites to avoid mimics. A little knowledge will go a long way towards providing the confidence you need to successfully navigate the open access environment.