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

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

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

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

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/

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: 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

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 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: 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/

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

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

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

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

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

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

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

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/

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