Courses & MOOCs
- Coursera — university courses and professional certificates (free audit on most).
- edX — courses from MIT, Harvard, and hundreds of partners.
- Khan Academy — K-12 through early college, practice and videos.
- MIT OpenCourseWare — free MIT course materials.
- OpenStax — peer-reviewed, free textbooks.
- Saylor Academy — free, self-paced courses (some ACE credit eligible).
- FutureLearn — short courses and online degrees.
- Alison — free courses with optional paid certificates.
- Class Central — meta-search across free and paid online courses.
- freeCodeCamp — full coding curriculum and certifications.
- The Odin Project — open-source web dev curriculum.
- Harvard CS50 — legendary intro computer science course, free.
- Stanford Online — free and paid courses from Stanford.
- Open Yale Courses — full recorded Yale lectures, free.
- OpenLearn — Open University’s free course library.
- Open Culture — curated free courses, audiobooks, and films.
- Udacity (free catalog) — smaller free library than it used to be, but still has solid intro tech content (most newer content is paid).
AI, Machine Learning & Data
- DeepLearning.AI — short courses and specialisations from Andrew Ng’s team (free to audit most).
- Hugging Face Learn — free, hands-on courses on LLMs, transformers, agents, and deep RL with certificates.
- fast.ai — Practical Deep Learning for Coders, free and still one of the best ML starting points.
- Google AI for Developers — Gemini, TensorFlow, and ML learning paths.
- Microsoft Learn — free role-based paths for Azure, AI, data, and dev.
- Kaggle Learn — fast, focused data science and ML micro-courses with notebooks.
- Anthropic Courses — free courses on prompting, building with Claude, and agent design.
Video Learning & Lectures
- TED — talks and TED-Ed lessons.
- CrashCourse — humanities, science, study skills.
- MinutePhysics — quick physics explainers.
- CGP Grey — maps, politics, concepts.
- 3Blue1Brown — visual math.
- Numberphile — numbers and puzzles.
- Veritasium — science and engineering.
- Kurzgesagt — animated big-idea explainers.
- TheNewBoston — programming tutorials.
Language Learning
- Duolingo — gamified fundamentals.
- Memrise — spaced-repetition vocab with native speaker video.
- Busuu — structured courses plus community feedback.
- italki / Verbling — 1-to-1 tutors with native speakers.
- Babbel — bite-size lessons.
- HelloTalk / Tandem — language exchange with natives.
- Clozemaster — vocab in context via sentence cloze drills.
- LingQ — read and listen with assisted transcripts.
- AnkiWeb — the king of spaced-repetition flashcards.
- Language Transfer — free audio courses with a thinking-method approach.
- Refold — immersion-based language learning methodology and community.
Books, Texts & Audiobooks
- Project Gutenberg — 75k+ public-domain ebooks.
- LibriVox — free public-domain audiobooks.
- Internet Archive — books, video, software, Wayback Machine.
- Open Library — borrow millions of ebooks.
- Standard Ebooks — beautifully formatted, carefully produced classics.
- Bartleby Lit Hub — the original free public-domain literature and reference archive (note: the rest of bartleby.com is now a paid homework service).
Programming & Computer Science
- Codecademy — interactive coding paths.
- MDN Web Docs — authoritative web docs and tutorials.
- web.dev — Google’s guide to modern web development.
- CSS-Tricks — deep practical front-end articles and guides.
- GitHub Skills — hands-on Git and GitHub courses.
- Exercism — free coding practice with human mentor feedback, 70+ languages.
- Roadmap.sh — community-built roadmaps for every dev role.
- Frontend Mentor — real-world front-end challenges with designs supplied.
- LeetCode / HackerRank / Codewars — coding practice and interview prep.
- CS50 — legendary intro CS covering C, Python, and web.
DIY & How-To
- Instructables — community projects and guides.
- wikiHow — illustrated how-tos.
- HowStuffWorks — how things work.
- Howcast — short how-to videos.
- Stack Exchange — expert Q&A communities across hundreds of topics.
Documentaries & Long-Form
- Kanopy — free with many library and university cards; high-quality library.
- Curiosity Stream — subscription documentary library.
- Top Documentary Films — curated free doc aggregator (ad-heavy).
General Knowledge, Quizzes & Research
- Wikipedia — still the web’s encyclopedia.
- Our World in Data — data-driven research and charts.
- Gapminder — global development data, tools, and teaching resources.
- Smithsonian Learning Lab — free resources from 21 Smithsonian museums.
- Google Arts & Culture — museum collections, virtual tours, and cultural stories.
- Mental Floss — trivia and explainers.
- Snopes — fact-checking.
- Sporcle — quizzes galore.
- Lizard Point — geography and more quizzes.
- FreeRice — learn and donate rice via the World Food Programme.
Math Tools & Problem Solving
- Wolfram|Alpha — computational answers.
- Project Euler — math and programming challenges.
- Desmos — graphing calculator and classroom activities.
- GeoGebra — interactive math apps.
- Brilliant — interactive math, science, and CS.
- Art of Problem Solving (AoPS) — advanced problem solving for strong students.
- Math Is Fun — approachable explanations and puzzles.
Science & Simulations
- PhET — interactive physics, chem, bio, and math sims.
- NASA — images, missions, curricula.
- Google Scholar — scholarly search.
- arXiv — open research preprints.
- DOAJ — directory of open-access journals.
Music Theory & Lessons
- JustinGuitar — free guitar curriculum, still the gold standard.
- MusicTheory.net — lessons, exercises, and tools.
- Ultimate Guitar — tabs and lessons.
- Teoria — theory and ear-training drills.
- Musicca — music theory practice.
Learn & Play Chess
- Lichess — free play, puzzles, studies, no paywall, ever.
- Chess.com Learn — interactive courses and lessons.
Words, Poetry, Etymology & Writing
- Online Etymology Dictionary — origins of words.
- Poetry Foundation — huge curated poetry library with poet profiles and essays.
- Genius — community-annotated lyrics and texts.
- Investopedia — finance explainers and dictionary.
- LessWrong — rationality and critical-thinking essays.
Note-Taking & Knowledge Management
- Zettelkasten.de — the definitive resource on the Zettelkasten method.
- Notion Academy — free lessons on building personal systems in Notion.
- Obsidian Help & Community — docs, plugins, and examples for the PKM power-user’s tool of choice.
Cooking & Kitchen Science
- Serious Eats — tested recipes and food science.
- Budget Bytes — tasty on a budget.
- Cooking for Engineers — technique-focused recipes.
- Reluctant Gourmet — fundamentals and methods.
Spotted a great site that should be here? Drop it in the comments and I’ll update the list.