Analyze Math: Tutorials, problems, worksheets, applets, etc.
Art of Problem Solving: A site that helps motivated students in Grades 5 to 12 become successful, creative problem solvers. Recommended for students who wish to excel.
Caribou Contests: “Caribou is an online educational platform offering math learning resources and competitions for students from the start of elementary school to the end of high school.”
Centre for Education in Mathematics and Computing at the University of Waterloo:
Contest problem links at Wild About Math!:
Cut The Knot: A beautiful site with a lot of interesting mathematics problems and puzzles. It is clearly a labour of love, written and compiled by the late Alexander Bogomolny.
Exercises in Math Readiness: University preparation from the University of Saskatchewan.
MIT Mathematical Problem-Solving course (Putnam Seminar): Intended for undergraduate university students.
Nick Hobson’s Mathematical Puzzles:
Spirit of Math: An enrichment site for high-performing elementary and high-school students.
CAP High School/Cegep Prize Exam:
Sir Isaac Newton Exam in physics, from the University of Waterloo.
Worked Examples in Physics: An extensive collection of worked examples for calculus-based first-year university physics, from the late David Murdock of Tennessee Technological University. There are also some worked examples for algebra-based first-year university physics.
Problem of the Week: From David Moran, Harvard University. These are advanced mathematics and physics problems, so go here for a challenge!