As described by Peter Suber, open access (OA) scholarship is "digital, online, free of charge, and free of most copyright and licensing restrictions."
Authors may make their work openly available by either placing their content in a repository ("green OA") or opting to publish through an OA venue ("gold OA").
Why open access?
Whether self-archiving or choosing to make your work openly available through a publisher, there are advantages for you to consider when openly distributing your work.
There are many useful search tools for your consideration when looking for open content.
Find open access ebooks in your disipline at the Directory of Open Access Books.
Search for open dataset repositories:
Subject repositories are open to scholars all over the world who publish work in a particular discipline. Some of the larger ones include: