Ken Duisenberg's Puzzle of the Week (Popularity: )

Problem archive and puzzle links.

Scott Kim (Popularity: )

Puzzles for web, computers, and print; ambigrams.

Math Puzzles (Popularity: )

Logic puzzles and riddles with some solutions.

Mathematics Problem Solving Task Centres (Popularity: )

Designed to assist teachers and students in problem solving. Includes problem of the month.

Mathpuzzle.com (Popularity: )

Celebrates math puzzles and mathematical recreations.

Hamline University (Popularity: )

Monthly problems.

Torus and Klein Bottle Games (Popularity: )

Collection of Java-based educational puzzles.

Baylor Problem of the Month (Popularity: )

Monthly problems with archive and results.

Macalester College Problem of the Week (Popularity: )

Weekly math problem and archive from Professor Stan Wagon for first-year college students presented by ...

Mathematical Recreations (Popularity: )

Detailed exploration of a selection of mathematical topics.

Problem of the Fortnight (Popularity: )

Monthly problems with archive and solutions.

Monthly Problem (Popularity: )

Math problems and solutions from Math Central.

Problem of the Week (Popularity: )

Sponsored by Shepherd College.