Baylor Problem of the Month  
   Monthly problems with archive and results.
   http://www3.baylor.edu/Math/problems.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

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/

Mathematics Problem Solving Task Centres  
   Designed to assist teachers and students in problem solving. Includes problem of the month.
   http://www.mav.vic.edu.au/PSTC/

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

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

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.
   http://mathforum.org/pow/

Problem of the Week Links  
   Links to problems of the week sites organized by grade levels.
   http://www.wits.ac.za/ssproule/pow.htm

Ole Miss Problem of the Week Contest  
   A weekly contest for all students from elementary to high school. Prizes awarded each month.
   http://www.olemiss.edu/mathed/contest/

IBM Research Ponder This  
   A monthly on-line competition hosted by researchers at IBM.
   http://www.research.ibm.com/ponder/index.shtml

Alvirne High School Problem of the Week  
   Calculus problems with archive and solutions.
   http://homepages.seresc.net/~sray/alvirne.html

Calculus-Help Problem of the Week  
   Calculus based problems range from easy to difficult.
   http://www.calculus-help.com/problem.html

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

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

Problem of the Week  
   Sponsored by Shepherd College.
   http://www.shepherd.edu/mathweb/problems.html

Hamline University  
   Monthly problems.
   http://www.hamline.edu/~math/aguetter/pom/prob_of_month.html

Math Forum: Geometry Problem of the Week  
   Past archive and solutions. Recieve help from mentor.
   http://mathforum.org/geopow/

Math Forum: Algebra Problem of the Week  
   Past archive and solutions. Recieve help from a mentor.
   http://mathforum.org/algpow/

Math Forum: Precalculus POW  
   Weekly math problems and solutions from Math Forum.
   http://mathforum.org/precalcpow/

Math Forum: Discrete Math Problem of the Week  
   Past problems and solutions, student Recognition.
   http://mathforum.org/dmpow/

Math Forum: Elementary Problem of the Week  
   A weekly interactive project for elementary school mathematics. Past problems, solutions, and student Recognition.
   http://mathforum.org/elempow/

AIMS Puzzle Corner  
   Provides monthly puzzles with the goal of creating an engaging learning environment.
   http://www.aimsedu.org/puzzle/

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

The Little Math Puzzle  
   The Little Math Puzzle has been a K-12 Internet activity since 1995 for grades 5-9. Currently the puzzles have ceased but the site maintains complete archives of past problems.
   http://www.sprucelog.com/lmp/

Purdue University Problem of the Week  
   Challenging problem open to college & pre-college students, faculty, and staff. Site also contains archive of past problems and solutions.
   http://www.math.purdue.edu/pow/pow.cgi

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

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