Learning, Knowledge & Data
41 sitesfreeCodeCamp
FreeFree coding curriculum, projects and certifications (nonprofit)
Information is Beautiful
FreeCases that turn the world's data into infographics
World Bank Open Data
FreeFree development and economic indicators for 217 countries
Google Dataset Search
FreeSearch that finds public datasets across the web
Internet Archive
FreeDigital library preserving books, video, music and web snapshots
Standard Ebooks
FreePublic domain e-books with polished proofreading and typesetting
WordReference
FreeMultilingual online dictionary and forum strong on examples and idioms
GeoGebra
FreeIntegrated math visualization tool for geometry, algebra, calculus and statistics
Wolfram Alpha
FreemiumKnowledge engine that answers natural-language questions with computation and data
Brilliant
FreemiumInteractive courses that teach math, science and CS through problem-solving
The Pudding
FreeInteractive visual essays combining data visualization and storytelling
Gapminder
FreeTools to correct global misconceptions with data (bubble charts, Dollar Street)
Our World in Data
Free14,000+ interactive charts on 126 topics under an open license
Public Domain Review
FreeUnearthing out-of-copyright sources with essays and 10,000+ public domain images
Etymonline
FreeScholarly etymology dictionary tracing English word origins and shifts in meaning
Stanford Encyclopedia of Philosophy
FreeFree peer-reviewed encyclopedia of philosophy
Seeing Theory
FreeProbability and statistics through interactive D3 visualizations (Brown University)
PhET
FreeInteractive physics, chemistry and math simulations from CU Boulder (Korean)
Monkeytype
FreeMinimal, customizable multilingual typing practice measuring WPM and accuracy
Omniglot
FreeEncyclopedia of the world's writing systems, languages and multilingual phrases
Language Transfer
FreeAudio language learning by the 'Thinking Method' (no ads, sign-up or fees)
Tatoeba
FreeOpen database of 13.5M example sentences and translations in 429 languages (audio, API)
Saylor Academy
Free160+ free self-paced courses with certificates and credit recognition
LibreTexts
Free2,000+ free open textbooks across 17 fields plus a homework system
Open Culture
FreeCurated free courses, audiobooks, documentaries and e-books from around the world