Virtual Reference Desk: Open Source Resources

"Open access is a broad international movement that seeks to grant free and open online access to academic information, such as publications and data. A publication is defined 'open access' when there are no financial, legal or technical barriers to accessing it - that is to say when anyone can read, download, copy, distribute, print, search for and search within the information, or use it in education or in any other way within the legal agreements."

--OpenAccess.nl

• The Directory of Open Access Journals: a resources of over 19,000 open access journals
• Directory of Open Access Books: a discovery service of over 67,000 open access peer-reviewed academic books
• arXiv: a repository of over 2 million scholarly articles in physics, mathematics, computer science, quantitative biology, quantitative finance, statistics, electrical engineering and systems science, and economics. These are not necessarily peer-reviewed.
• SSRN (formerly Social Science Research Network): "research platform used to share early-stage research, evolve ideas, measure results, and connect scholars around the world"
• CORE: bills itself as "the world's largest collection of open access research papers"

Open Access has different colors to signify the different access rights a user has to an open source article or manuscript. In order to properly interpret the rights of each color, users must understand the different versions an article or manuscript go through.

1. Pre-print: This is the original manuscript submitted to the publisher before peer-review, formatting, or copy-editing by the publisher.
2. Post-print: This is the manuscript accepted for publication; it has been peer-reviewed and copy-edited but not yet formatted.
3. Publisher's final version: This is the version that is printed or published, fully reviewed, edited, and formatted.

Visit this explanation of the different colors of Open Access from Old Dominion University.