100 Search Engines for Academic Research

• A list of search engines and other sites to use for academic searching

101 Free Online Journal and Research Databases for Academics

• A list of free to use directories, databases, and repositories to find free and open scholarly research

Creative Commons

• A non-profit organisation who provide licences that allow content to be modified, adapted or "remixed" once credit is attributed to the original creator

Digital Public Library of America

• A free, online library that provides access to millions of books, photographs, maps and audio-visual materials and more from libraries, museums and archives across the United States

ERIC

• The Education Resources Information Center (ERIC) is an online digital library of education research and information sponsored by the Institute of Education Sciences (IES) of the U.S. Department of Education. Some full text is freely available.

Legamus

• A growing collection of free audio books from texts that are in the public domain in Europe

LibreVox

• A growing collection of free audio books from texts that are in the public domain in the US

OAButton

• In addition to using the browser extensions, you can also search for free and legal articles using this site

Open Access Scholarly Publishers Association

• A group representing Open Access publishers. It promotes education about OA and sets standards for ethics and best practice. As with DOAJ, criteria for inclusion must be met, making OASPA is a useful resource for researchers to assess the quality of a journal.

Open Culture

• Brings together high-quality cultural & educational media for the worldwide lifelong learning community. Content includes online courses, audiobooks, ebooks, textbooks and much more.

Open Textbook Adaptation Guide

• For any teachers interested in OERs, this is a guide to customising open textbooks

Preprint server list

• A curated list of preprint servers

Project Gutenberg

• A library of over 60,000 free eBooks, that can be downloaded in a number of different formats or read online.

ProQuest PQDT Open

• ProQuest are a commercial outfit, but this database of open access dissertations and theses is freely available

Science.gov

• A web portal and specialised search engine for United States government scientific and technical information and research that includes some full text

Self-Publishing Guide for Open Textbooks

• A reference for individuals or groups wanting to write and self-publish an open textbook

WorldwideScience

• A global science gateway comprised of national and international scientific databases and portals, or more simply put, it's a search engine that returns academic results from a variety of different databases and portals.