Khan Academy offers a vast collection of free instructional videos, practice exercises, and learning materials across subjects such as math, science, history, and economics. While the content is not openly licensed for modification, it is freely accessible for learners worldwide.

Developed by Rice University, OpenStax provides free, peer-reviewed, high-quality textbooks that are openly licensed under Creative Commons. These textbooks are widely used in higher education and can be modified to fit course needs.

Massachusetts Institute of Technology (MIT) offers MIT OpenCourseWare, a comprehensive library of free course materials, including lecture notes, assignments, and exams from actual MIT courses. These materials are openly licensed for use and adaptation.

Saylor Academy provides full online courses with open textbooks, assessments, and certifications. These courses span multiple disciplines and are freely available for learners and educators.

CK-12 offers free, customizable, and interactive textbooks (FlexBooks) in STEM and other subjects for K-12 and higher education. These resources allow teachers to adapt content to their specific classroom needs.

CK-12 offers free, customizable, and interactive textbooks (FlexBooks) in STEM and other subjects for K-12 and higher education. These resources allow teachers to adapt content to their specific classroom needs.

A Wikimedia project, Wikibooks provides a collection of open-content textbooks that anyone can edit and improve. It covers a range of subjects, making it a dynamic and evolving repository of learning materials.

Developed by the University of Colorado Boulder, PhET provides free, interactive math and science simulations designed for students of all levels. These simulations allow learners to explore physics, chemistry, biology, earth science, and mathematics concepts in an engaging, game-like environment.

The Concord Consortium offers a vast collection of free, research-based interactive simulations in STEM education. Topics include molecular dynamics, genetics, energy transfer, and more. Many of these resources integrate well with learning management systems and classroom instruction.

Desmos is a powerful, free graphing calculator and math exploration tool that enables students to visualize equations, create interactive graphs, and explore mathematical concepts dynamically. It is widely used in classrooms for algebra, calculus, and beyond.

GeoGebra offers free online tools for interactive mathematics, including graphing, geometry, algebra, and calculus. It provides a range of dynamic visualizations that support inquiry-based learning and student engagement.

In addition to its open textbooks, CK-12 provides interactive simulations, including virtual labs, 3D models, and adaptive learning exercises. These resources help students grasp STEM concepts through experiential learning.

NetLogo is an open-source simulation platform that allows users to explore complex systems and behaviors in fields like biology, physics, and social sciences. It is particularly useful for computational modeling and agent-based simulations.

Molecular Workbench from the Concord Consortium provides interactive, research-based molecular simulations in chemistry and biology. Students can manipulate molecules, test hypotheses, and observe reactions in a virtual lab setting.

Virtual Microscope provides access to high-resolution digital microscope slides, allowing students to explore biological specimens without needing a physical microscope. Its widely used in biology and medical education.

MIT OpenCourseWare is one of the most well-established open educational resources. It offers lecture notes, assignments, exams, and even some recorded lectures from actual MIT courses. Topics range from engineering and science to humanities and social sciences.

Carnegie Mellons Open Learning Initiative provides openly licensed online courses in subjects like statistics, biology, and computer science. The courses are designed with built-in learning analytics to help students track their progress.

edX offers online courses from top universities like Harvard, MIT, and Berkeley. While certification typically requires payment, many courses allow free access to lectures and course materials. Some edX courses can be credited toward degrees.

FutureLearn provides free courses from universities worldwide. Learners can access video lectures, discussions, and activities for free, with the option to pay for certificates or extended access.

Yale University offers free access to high-quality lecture recordings, transcripts, and course materials from a variety of disciplines. Unlike some MOOCs, Open Yale Courses do not include quizzes or assessments but provide full lecture series from renowned professors.

Delft University of Technology in the Netherlands offers OpenCourseWare in engineering, sustainability, and technology fields. These courses include lecture materials, assignments, and projects.

OpenLearn provides free courses across a broad range of subjects, including history, education, health, and science. Many courses include interactive activities and self-assessment tools.

The Directory of Open Access Journals is a comprehensive database of peer-reviewed open access journals covering a wide range of academic disciplines. It provides researchers and educators with access to thousands of high-quality, freely available scholarly articles, ensuring that knowledge is widely shared and accessible.

Managed by the U.S. Department of Education, ERIC is a central repository for research related to education, including journal articles, conference papers, and reports. It serves as a valuable resource for educators, instructional designers, and policymakers seeking research on teaching methods, learning outcomes, and educational technology.

A service of the U.S. National Library of Medicine, PubMed Central provides free access to full-text biomedical and life sciences research articles. It is an essential resource for students, faculty, and researchers in health sciences, nursing, and medicine, offering a wealth of peer-reviewed studies.

Operated by Cornell University, arXiv is an open-access repository that houses preprints and published research in fields such as physics, mathematics, computer science, quantitative biology, and engineering. It is widely used by academics and researchers to share their work quickly and openly.

A project of the Wikimedia Foundation, Wikimedia Commons hosts millions of freely usable media files, including photographs, illustrations, and diagrams. Many images are available under Creative Commons licenses, allowing educators and students to integrate them into their work with proper attribution.

Pixabay offers a vast collection of high-quality public domain images, illustrations, and vector graphics. All content on Pixabay is free to use for educational and commercial purposes without attribution, making it an excellent resource for course materials and multimedia projects.

A popular source for high-resolution photography, Unsplash provides stunning visuals that are free to use without restrictions. While primarily known for artistic and landscape photography, it also includes educational and conceptual images useful for presentations and digital content creation.

For icons, symbols, and vector graphics, The Noun Project offers a vast library of free and openly licensed icons. These can be used in presentations, infographics, and instructional materials to enhance visual communication. Some icons require attribution, but many are available for unrestricted use.