Stony Brook Problem of the Month
- Monthly math challenge with past problem archives and solutions, and hall of fame.
- http://www.math.sunysb.edu/monthly-problem/

IBM Research Ponder This
- A monthly on-line competition hosted by researchers at IBM.
- http://researchweb.watson.ibm.com/ponder/

Mathematics Problem Solving Task Centres
- Designed to assist teachers and students in problem solving. Includes problem of the month. Paid membership is required to view archived problems.
- http://www.mav.vic.edu.au/members/problems.html

Math Forum: Math Fundamentals Problem of the Week
- A weekly interactive project for elementary school mathematics. Past problems, solutions, and student recognition. Paid membership required to view problems.
- http://mathforum.org/funpow/

Math Forum: Discrete Math Problems of the Week
- Past problems and solutions, student recognition. Paid membership required to view problems.
- http://mathforum.org/library/problems/discrete.html

PuzzleUp
- Weekly math problem with archive and scoreboard.
- http://www.puzzleup.com/

Purdue University Problem of the Week
- Weekly math challenge with past problem archives and solutions.
- http://www.math.purdue.edu/pow/

Trent University Problem of the Week
- Weekly math problems and solutions from Trent University.
- http://euclid.trentu.ca/math/dgp/potw_main.html

Bradley University Problem of the Week
- Weekly math problem and archive from Professor Alberto L. Delgado.
- http://bradley.bradley.edu/~delgado/potw/potw.html

Dansmath Problem of the Week
- Weekly math problem, with solutions, archive, and leader board.
- http://www.dansmath.com/probofwk/probofwk.html

John Handley High School Problem of the Week
- Weekly math problem with solutions and archive.
- http://www.pen.k12.va.us/Div/Winchester/jhhs/math/probweek/probweek.html

Problem of the Month
- Posted by the Mathematics Department of Bilkent University.
- http://www.fen.bilkent.edu.tr/~cvmath/Problem/problem.htm

Math Forum: Algebra Problem of the Week
- Past archive and solutions. Receive help from a mentor. Paid membership required to view problems.
- http://mathforum.org/algpow/

Math Forum: Geometry Problem of the Week
- Past archive and solutions. Receive help from mentor. Paid membership required to view problems.
- http://mathforum.org/geopow/

Math Magic
- Devoted to original mathematical recreations with puzzles and links.
- http://www.stetson.edu/~efriedma/mathmagic/

Ken Duisenberg's Puzzle of the Week
- Problem archive and puzzle links.
- http://ken.duisenberg.com/potw/

Math Forum: Problems of the Week
- Projects from the Math Forum presenting weekly interactive math challenges to accumulate points for bronze, silver and gold prizes. Individual or class participation. Paid membership required to view problems.
- http://mathforum.org/pow/

Problem of the Fortnight
- Twice-monthly problems with archive and solutions.
- http://persweb.wabash.edu/facstaff/axtellm/fortnight/fortnight.html

Monthly Problem
- Math problems and solutions from Math Central.
- http://mathcentral.uregina.ca/MP/current/

Macalester College Problem of the Week
- Weekly math problem and archive from Professor Stan Wagon for first-year college students presented by the Math Forum.
- http://mathforum.org/wagon/