Many academic institutions have joined the Budapest Open Access Initiative (BOAI) which defines "open access" as follows:
By "open access" to this literature, we mean its free availability on the public internet, permitting any users to read, download, copy, distribute, print, search, or link to the full texts of these articles, crawl them for indexing, pass them as data to software, or use them for any other lawful purpose, without financial, legal, or technical barriers other than those inseparable from gaining access to the internet itself. The only constraint on reproduction and distribution, and the only role for copyright in this domain, should be to give authors control over the integrity of their work and the right to be properly acknowledged and cited.
In addition to benefiting consumers of scholarly information, open access also benefits scholars, increasing the visibility, influence, and potential benefit of their research. It helps redress global inequity of access to scholarship by dismantling cost barriers to research dissemination. And it returns research results more swiftly and readily to the public, who provide much of the funding for scholarly work.
Peter Suber's explanations of open access are both concise and insightful: a) Open Access Overview; and A Very Brief Introduction to Open Access. Particularly apt is his observation (from Open Access Overview) that
OA is compatible with copyright, peer review, revenue
(even profit), print, preservation, prestige, career-advancement,
indexing, and other features and supportive services associated with
conventional scholarly literature. . . . . The primary difference is that the bills are not paid by readers and hence do not function as access barriers.
To read more views, announcements etc. of Peter Suber and others consult the Open Access Tracking Project (OATP).
Examples of common Open Access (OA) practices on college campuses include