This is a list of high-quality online resources that are good to know about but hard to stumble across.

Maybe they aren’t maintained often but remain relevant. Maybe they’re personal blogs with good content but few keywords.

Whatever the reason, this is their place to shine.

Rules for Inclusion

1. Only free resources.
2. Some degree of obscurity required. They shouldn’t be the first thing you see when you search something like “biology.”
3. No resources for which strictly-better alternatives exist.

Have something to add? Submit an article here.

Is a link broken? Let me know!

Encyclopedias

• Wikipedia Contents – Wikipedia’s Table of Contents
• Wikipedia Main Topic Classifications – Wikipedia’s topic classification à la the Dewey Decimal System or the Propaedia.
• Encyclopedia Britannica Alphabetical Browse – Britannica’s alphabetical index. Britannica tries to balance its scope disadvantage compared to Wikipedia with an emphasis on authority and strong tone. While the accuracy of the two works is about the same, Britannica has better prose.
• Golden – Hard to describe; it’s a bit like a Web-3.0 iteration of Wikipedia. Highly active as of August 2022.
• Specialty Dictionaries – Specialty dictionaries on every subject.

Books

• Greater Books – This union of many “great books” lists also tracks which books make the cut most often.
• The Greatest Books – Ditto, but with more lists and less editing.
• Faded Page – A Canadian eBook archive.
• Oxford Reference – Offers previews of today’s best print reference works.
• Google Books – An attempt to catalog every book ever written. Offers previews of many of them.

Class Notes and MOOCs

• MIT OCW – Class notes from MIT'

Charts and Diagrams

• Diagram Repository - Repository of diagrams a friend of mine made

Journals

• Directory of Open Access Journals

Miscellany

• Internet Search Tips
• Web Whiteboard – A whiteboard web app. I like this for conferences and Zoom calls.
• LessWrong – Online forum dedicated to improving the art of human cognition. Mainly focused on AI, but there’s also plenty of discussion on subjects like physics, computer science, and cognitive science.
• Bozeman Science – Great resources for the high school curriculum.
• DIYGenius – Online self-education website.
• Piero Scaruffi’s Knowledge Base – It may be easier to list the subjects this blog does not cover. Scaruffi is one of the most prolific writers on the web.
• Nintil – Longevity, philosophy, social science, and more…

Other Lists

• Wikipedia’s List of Free Online Resources

Textbook Archives and Repositories

• Open Textbooks – Textbooks in the public domain
• Saylor Academy – More public-domain books and knowledge resources
• Open Textbook Library – Ditto
• CNX OpenStax – OpenStax textbooks were written for the public domain.

Specific Subjects

History

• Best History Sites – A general history website index.
• World History Encyclopedia – Expert-driven
• Map of Contemporaries – I love this site. Breaks through the vertical, chunk-by-chunk rendering of history to reveal the parallelism that lies beneath. Reminds you of two things: first, that history happened all at once – Lincoln and Bismark were contemporaries – and second, that most history is recent – Napoleon’s death was only three lifetimes ago.
• World History Maps – Learn which far-flung civilizations were contemporaries.
• European Historical Maps – Historical maps focusing on Europe
• Pantheon – Beautiful data visualizations of history’s most important places, people, and ideas.
• Christopher Witcombe’s Art History Resources
• US History
• Learn Hieroglyphs
• History of War – Covers military history
• The Pirate King – Covers the Golden Age of Piracy
• Writing a Good History Paper

Geography

• The CIA World FactBook – Database of the world’s states, nations, and regions.
• GeoCurrents – Geography website index.
• David Rumsey Map Collection – General resource for historic atlases.

Note: I don’t list them here because they tend to be overly specific, but university map collections are great for rare historical and geographical information.

Arts and Culture

• Artcyclopedia – A searchable database of art, my favorite on the web
• WikiArt – Wikipedia for art
• Just SketchMe – You know the little wooden mannequins artists pose as character references? There’s an app for that. This is the app.
• Drawabox – Free drawing lessons and exercises with a thriving community to match.
• C. Bargue Drawing Course – Traditional sketches to copy and learn from.
• Design is Fine. History is Mine. – A searchable database of design.
• Butterick’s Practical Typography – An online, interactive, free-to-use typography textbook. The best of its kind. (As far as I can tell, the only of its kind.)
• Visual Arts Encyclopedia – I can’t vouch for whether it’s up-to-date, but it has the typical advantage over Wikipedia of a stronger voice.
• Character Design References
• Vishopper – Real-life figure references for artists.
• PokeCommunity Art Tutorial – A great digital art tutorial from the Pokémon community
• Crimson Daggers Art Forum
• Great English Churches – A businessman-turned-church tourist roams England to catalog its rich architectural heritage.

Music and the Performing Arts

• Music Theory – The web’s canonical music theory resource.
• IMSLP – The canonical source for sheet music.
• 8notes – Sheet music and an app to play it.
• Piano Lessons – Free piano lessons
• 52 Composers – Covers the essential composers and their works.
• ABC Notation – ABC notation can render music fully in ASCII. This website catalogues ABC-notated songs, especially folk songs.
• Similar Songs Finder

Literature

• The Literature Network – A literature forum.
• The Phrontistery – Rare words, lost words, studying words, carrying words, color words, nonsense words, speech styles, units of measurement. This site’s scope and quality inspires awe, opening the websurfer’s eyes to the cacophonous diversity of English.
• The Writing Center – A general paper-writing resource.
• Online Etymology Dictionary – Comprehensive and very high quality.
• Silva Rhetoricae – A nice, introductory resource on rhetoric.
• Shakespeare Online – Analyses, quotations, sources, etc.
• Urbigenous – A nice little collection of works. Focuses on science fiction and cyber culture.

“Classic” or “Great” Books

• Global Language Resources – Books rendered in eye-dazzling DJVU format.

Poetry

• Poetry Foundation – Poems, often with commentary
• Famous Poets and Poems
• Modern American Poetry

Other Art and Culture

• Sensei’s Library – Covers the abstract board game Go.
• Tel’s Go Notes – Similar concept by a single person. Includes sample games and commentary.
• ChessOps – An online openings textbook.
• Image Placeholders – For under-construction webpages

Practical Skills

Skills that aren’t taught in school but are still important, such as soft skills, survival skills, home economics, and self-management.

• Wilderness Survival – A general guide
• Survivor Library – Apocalypse preparation library
• Skills You Need – Life skills
• The Adequate Life Guide – Distills the self-help genre into a palm-sized handbook
• Army Publications – Logistics publications by the United States army

Natural Sciences

• Milan Cvitkovic’s Science Blog

Biology

• Encyclopedia of Life – A global database of Earth’s life
• The Bio-Web – A collection of biology websites
• The University of Arizona Biology Project – A general resource for introductory biology
• InnerBody – Safety research on home health products
• Animal Diversity Web – Encyclopedia of Animal Diversity
• The Microbiology Information Portal
• iBiology – Biology talks

Medicine

• Drugs.com – Info on drug safety, interactions, and side effects
• WebMD – Online compendium of medical information

Psychology

• Optical Illusions – A very large collection of optical illusions of all kinds.

Sociology

• Research Areas and Topics – NORC – The University of Chicago’s statistical sociology lab

Political Science

• Political Resources – Small political government blog

Economics

• Free Econ Help – Questions and homework solutions database
• Investopedia – Thorough, well-written articles on economics, finance, and investment
• Online Economics Encyclopedia

Legal Science

• Wex – Legal dictionary and encyclopedia by the Legal Information Institute at Cornell
• Nolo’s List of Helpful Websites
• Justia Legal Guides – Database of case law from throughout the US

Languages and Linguistics

Latin

• PHI Latin Texts – Repository of original Latin texts
• Online Latin Dictionary – Includes thorough conjugation tables and a great engine for simple searches
• Joseph Susanka’s Silva – The best Neo-Latin database I know of
• Bennet’s Latin Grammars – A ready and able reference
• Vocabula computatralia – Computer vocabulary in Latin

French

• Tex’s French Grammar – Great lessons from UT Austin
• ToLearnFranch – Quizzes, lessons, etc.

The Physical Sciences

Astronomy

• Astronomy Notes – Notes for the introductory astronomy course

Earth Sciences

• geology.com – Comprehensive, well-written, and continuously updated
• BriteCo's Geology Links – A list of geology and gemology-related resources
• World Weather Information Services – See forecasts across the globe from the World Meteorological Organization
• Gemology Course – Excellent lessons and web essays on gemology

Physics

• PHeT Simulations – Simulations of every physical phenomenon
• The Feynman Lectures on Physics – The most famous physics lectures of all time made available for free on the web
• The Physics Classroom – Textbook lessons, problems, and solutions
• Stack Exchange Compendium of Fantastic Physics Folios
• Another Partially-Overlapping List of Fantastic Physics Folios from the Physics Stack Exchange

Blogs

• Physics Insights – A miscellany brimming with excellent work
• How to be a GOOD Theoretical Physicist – A handbook for a novice physicist by Gerard ’t Hooft
• Of Particular Significance – Conversations About Science with Theoretical Physicist Matt Strassler
• Stan’s Hub – Blog by physicist Stanislav Sykora

Chemistry

• PTable – The web’s premier periodic table
• The PubChem Project – An online database of chemicals, their structures, and their properties.
• Illustrated Glossary of Organic Chemistry
• eCrystals – An archive of crystal structures generated by the Southampton Chemical Crystallography Group
• learnchem
• The Catalyst – Chemistry resources for teachers
• R. Stenutz’s Homepage – Chemical tables and more

Philosophy

• Stanford Encyclopedia of Philosophy – A truly academic publication available for free on the web.
• Internet Encyclopedia of Philosophy – Ditto
• The Basics of Philosophy
• Philosophers
• Muslim Philosophy Online
• David Pearce – This philosopher wants to neurochemically abolish human suffering.

Mathematics

• Desmos Graphing Calculator
• GeoGebra – 3D Graphing Calculator
• Cut the Knot – Thousands of mathematical puzzles, problems, and essays by Alexander Bogomolny
• Nick’s Mathematical Miscellany – Ditto from Nick Hobson
• The Math Page – Math textbooks by Lawrence Spector
• Paul’s Online Math Notes – Fantastic online textbooks for early college-level mathematics
• The Tilings Encyclopedia
• The Proof Wiki
• Mathwords – A mathematical glossary
• Planet Math – A forum
• Timeline of Mathematics – Important figures in math and when they lived
• CodeCogs LaTeX Equation Editor – Render ( LaTeX ) easily
• detexify – Another tool to find the ( LaTeX ) equivalent of a given symbol.
• Wolfram Alpha – Computational intelligence
• Archimedes Lab Project – A great math blog

Logic

• The Many Worlds of Logic – Lectures, notes, and logic exercises
• The Open Logic Project – Advanced mathematical logic materials

Religion and Mythology

• Religious Studies Web Guide – A comparative religion primer
• Internet Sacred Texts Archive

Abrahamic Religions

Christianity

• The Holy See
• The Catholic Encyclopedia
• Open Bible – Data from the Bible, including a useful concordance to locations
• Bible Gateway – The Bible and study resources
• Biblical Hermeneutics – Resources on interpreting the Bible

Islam

• The Noble Quran – Complete with translations and audio
• Sunnah Online – A blog and general resource for Islam
• Islam Question and Answer
• The Quranic Arabic Corpus – Annotations on Arabic grammar and morphology for each word of the Quran

Judaism

• Judaism 101 – Basic facts on Judaism
• The Jewish Website – A Jewish website

Other Religions

Buddhism

• Buddhanet – Buddhist texts, commentaries, meditations, and audio
• His Holiness The 14th Dalai Lama – The Dalai Lama’s Website
• Access to Insight – Readings in Theravada Buddhism

Hinduism

• All About Hinduism – Sri Swami Sivananda’s Primer on Hinduism
• The Bhagavad Gita – With commentary from Swami Mukundananda

Mythology

• Encyclopedia Mythica
• Theoi Greek Mythology – Likely the most comprehensive Greek mythology resource on the web
• Ancient Egypt: the Mythology – Ditto for Egyptian Mythology

Puzzles

• WU Riddles and Puzzles

Puzzlehunts

I’m obsessed with puzzlehunts and have therefore collected a disproportionate number of websites on them.

Let’s define a “puzzlehunt” as any self-contained group of sequential puzzles that don’t always fall into well-established formats like Sudoku or Masyu.

• Introduction to Puzzlehunts
• List of Puzzlehunts – A semi-comprehensive list of the best of the best. I list below only the ones that aren’t covered here.
• MIT Mystery Hunt Puzzle Index – Index by topic of puzzles from all the MIT Mystery Hunt iterations. An excellent resource for ideas and practice.
• Boston Area Puzzle Hunt League
• DASH – Different Area, Same Hunt
• Puzzled Pint – Smaller puzzlehunts

Asynchronous Puzzle Hunts

These puzzlehunts never ran on a specific date, having sprang fully-formed from the minds of their creators. They now exist embedded in a timeless void of infinite replayability.

• Rankk – A puzzle-solving sequence and the forum that surrounds it.
• The Order of the Octothorpe – Ditto
• Truly Kryptic – Ditto
• Perplex City Card Catalog – An ARG released by Mind Candy in the early 2000s. Each card featured its own puzzle with varying difficulty. The two hardest cards required respectively a proof of the Riemann Hypothesis and fifteen years of machine learning advancement to solve.
• Mezzacotta Puzzle Hunt
• Bongard Problems – An interesting category of problems researched by Harry Foundalis
• The Grey Labyrinth – An undead (dead in that it’s no longer active, alive in that the site is still up) puzzlehunting forum.