Game theory
Nice illustrations of sequential Prisoners Dilemma and the evolution of cooperation, Schellings Seperation theorem, and a lot of other neat games
Free textbooks for Decision and Game Theory by Giacomo Bonanno
The treasure trove that is Ariel Rubinstein's website: Free textbooks, Cafe guides, PhD advice, and much more
Statistics, Probability, and Data Visualizations
Why summary statistics and boxplots are insufficient to understand your data
Simpsons paradox, Local regression, and other educational gifs (+R code)
Visual explanation of the Central Limit Theorem
Visualization of how adding controls changes your slope (and "partial" predicted value)
Seeing Theory: Interactive and visual introduction to probability and statistics from rolling dice to Anscombe's Quartet
"Causal Inference: The mixtape" is a great textbook with STATA examples by Scott Cunningham
Differences in preferences for risk, trust, altruism, reciprocity and patience around the world
Fabulous website with research and data visualizations covering wide range of topics related to global development
Interactive graphs that allow to explore truth-telling/Lying behavior across different countries, incentive levels, subject pools, and experimental paradigmes