Khan Academy offers free online courses with video lessons and practice exercises in mathematics, physics, chemistry and other subjects.
GeoGebra is a free platform for creating and exploring interactive mathematics visualizations and geometric constructions.
Desmos is a free online graphing calculator and mathematical visualization tool for exploring functions and equations.
Seeing Theory is a visual and interactive introduction to probability and statistics concepts with interactive chapters.
Dictionary of mathematical terms and definitions with brief explanations.
Mathematics problems and articles from Cambridge's NRICH and Plus platforms, covering applied mathematics and problem-solving.
Website with interactive explanations, animations, and simple problems covering elementary to secondary mathematics.