There are two main ways to publish in open access: the gold road and the green road.
In both cases, the peer review process is of particular importance in ensuring the quality of journal articles.
The gold road: The article is available free of charge on the journal’s website. The journal can be an open access journal or a subscription journal that makes some individual articles freely accessible to the readers (these are commonly known as hybrid journals).
Although this is often the case, open access journals do not always require a financial contribution from the author in order to publish the article. Several business models exist, yet the articles are always available free of charge to readers. To find an open access journal, consult the Directory of Open Access Journals (DOAJ).
As for hybrid journals, the author usually pays in order to make his article available in open access. However, libraries often have to maintain their subscription to the journal so they still have access to all of the published articles.
For the scientific community:
The green road: The authors publish an article in an academic journal and self-archive a copy of the article in an open archive (ex.: arXiv.org) or institutional repository (PolyPublie). Many publishers do allow archiving of peer-reviewed articles (the final manuscript or the version formatted by the publisher). Some articles can be archived only after the embargo period expires. Authors must read their contracts, or the authors guidelines typically published in an editor's website, to be aware of their publisher's self-archiving conditions. As for articles submitted in PolyPublie by Polytechnique's authors, the library will validate self-archiving conditions and required embargos.
The Sherpa/Romeo website is a good starting point, because it includes a summary of archiving permissions and links to publishers' policies.
Author addendum to publication agreement
Did you know that you can make changes to a contract you sign with a publisher? In order to do this, you can add an addendum to the publication agreement.
Here is an example: the Canadian Author Addendum to Publication Agreement, proposed by the Canadian Association of Research Libraries (CARL). This document was adapted from the U.S.' Scholarly Publishing and Academic Resources Coalition (SPARC)'s addendum.
For more information on how to use it, consult the CARL Guide to Using the Canadian Author Addendum to retain your rights as the author of a journal article or book chapter.
Publishers with questionable credibility
Have you ever been approached by a journal wanting to publish your article in open access, subject to the payment of certain costs? Although there are many publishers that publish quality open-access journals, some take advantage of it by creating journals without scientific basis for their own gain. They are called predatory publishers.
Jeffrey Beall, an American librarian interested in open access, compiles a list of "questionable, scholarly open-access publishers", which is regularly updated. Click here to consult it.