algebra

MathBox: Tool for Thought (Algebra & Fourier Analysis)

blockchain

Blockchain Demo - A visual demo of blockchain technology
#1 Solidity Tutorial & Ethereum Blockchain Programming Course | CryptoZombies

calculus

An Interactive Introduction to Fourier Transforms

complex analysis

Complex Analysis

complexity science

Complexity Explained

cryptocurrency

#1 Solidity Tutorial & Ethereum Blockchain Programming Course | CryptoZombies

cryptography

the cryptopals crypto challenges

drawing

ZygoteBody for learning human anatomy

geography

The True Size Of Nations

learning

How to remember anything forever-ish

machine learning

Neural Network Playground

mathematics

An Interactive Introduction to Fourier Transforms
Parallel
Seeing Theory
Euclidea: Interactive geometric puzzles
Mathigon

music

Get started | Learning Music (Beta)
Every Noise At Once

music theory

Phrases and Cadences
Get started | Learning Music (Beta)
Music Theory Lessons - LightNote
Musical Chord Progression Arpeggiator - Outpan

oceans

The Deep Sea

philosophy

The History of Philosophy

physics

Physics Classroom

programming languages/clojure

4Clojure

programming languages/python

CheckiO | Python Online Playground
CodeSkulptor3
Python Tutor | Visualize Python Code Execution

programming languages/r

Swirl: Learn R, in R.

programming languages/rust

GitHub - rust-lang/rustlings: Small exercises to get you used to reading and writing Rust code!

programming languages/scratch

Scratch Homepage

programming languages/sql

The SQL Murder Mystery

quantum computing

Quantum Computing for the Very Curious

spaced repetition

How to remember anything forever-ish

transform calculus

An Interactive Introduction to Fourier Transforms