Authors can make their articles and other works freely available to the public by sharing them in an open repository. The UVA institutional repository Libra hosts scholarly works (including articles, data, and other materials like posters and presentations) created by scholars affiliated with UVA.
Other repositories focus on work from particular disciplines, or work funded by particular agencies (such as PubMedCentral, which accepts OA deposits for the National Institutes of Health and several other federal agencies).
Some repositories are focused on "preprints" – work that has not yet been peer reviewed (such as ArXiv, which caters to several STEM fields).
Journals have varying policies on use of repositories. Sherpa/Romeo is a good starting place for researching journal policies.
Academic social networks, such as Academia.edu and ResearchGate, differ from open access repositories. They are typically operated on a for-profit basis and do not have the same preservation commitments as repositories hosted by academic institutions. The following articles provide more information about these distinctions.
A Social Networking Site is Not an Open Access Repository
This 2015 article from Katie Fortney and Justin Gonder at the UC Office of Scholarly Communications contrasts the features of social networks like ResearchGate and Academia.edu with those of open access repositories.
Academia, Not Edu
This 2015 blogpost by Kathleen Fitzpatrick outlines her concerns with sharing scholarship via Academia.edu.
Fully Open Access Journals (sometimes called "Gold OA")
Fully OA journals publish their final versions online, free to access, and typically with an open license that enables reuse.
Some of these journals charge a fee (see Paying for OA below), but many do not.
"Hybrid" OA
Hybrid journals are published using a "traditional" subscription model, but will publish particular articles on an open access basis in exchange for a fee.
Critics accuse hybrid journals of "double-dipping" – charging open access fees to authors while continuing to charge the same (or more) in subscription fees to libraries. Many funders and universities will not pay or subsidize fees for open access in hybrid journals.
Paying for OA
Open access publishing, whether through repositories, journals, or other platforms, requires financial support. Technical infrastructure, administration, and other costs of publication can be significant. In a toll access model, the publisher collects subscription fees in exchange for access to the literature and uses those fees to cover its costs (plus, in some cases, a hefty profit). In an open access model, publishing costs (and, in some cases, more hefty profits) can be covered in a variety of ways.
Diamond OA (Free to read, free to write): in a Diamond Open Access model, neither authors nor readers pay directly. Instead, the cost of publishing is covered by a third party – an institution, agency, scholarly society, or other entity with an interest in supporting the publishing enterprise. SCOAP3 is an early success story for Diamond OA publishing.
APCs: Author Pays
One of the first models proposed for funding open access was to "flip" traditional publishing from a reader-pays model to an author-pays model.
In this model, the author pays an “article processing charge” to the publisher in exchange for open access publication.
Sometimes these fees can be included in grant awards as part of the cost of a research project, especially where the funder values open access to the results of its funded projects. Note that The Library does not pay or subsidize individual APCs or other OA fees, except under Read and Publish Agreements (see above, "Know Your OA Options").
Accordingly, this model has been more successful and has become more widespread in fields where grant funding is common.
Read and Publish Agreement
"Read and publish" agreements (also known as "publish and read," "transformative," and even just "OA agreements") are contracts that universities sign with publishers where APCs are waived or reduced for an institution's authors.
Authors usually must be the corresponding author of a manuscript to qualify. Publishers usually present a waived or reduced APC after the corresponding author discloses their affiliation with a qualifying institution.
These agreements provide some authors with a relatively seamless option to make their work OA, but the long-term affordability and equity of these types of contracts is yet to be determined.