Dick's Math Puzzle Page - A collection of mathematical puzzles, some original, with fully worked solutions. - http://www.mod2.org/

Mathematical Games - A collection of pencil and paper games with mathematical content. Many can be played through the site. - http://www.madras.fife.sch.uk/maths/games/

Problem Solutions - Archive of problems and solutions, compiled by Dr Alec Mihailovs of Shepherd College. - http://www.shepherd.edu/mathweb/solutions.html

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/

Downloadable and online games - A variety of Flash- and Java-based games and puzzles. - http://www.gameintellect.com/

Group Games - Animations that develop the theory behind such puzzles as the Rubik cube. - http://www.dmi.units.it/~logar/duek2/index_engl.html

Nandor's Exhaustive Chemical Words Pages - Lists all the English words, word squares, and magic squares that can be written using chemical symbols. - http://www.wellington.org/nandor/chemwords/chemwords.htm

Puzzles of Leonid Mochalov - A variety of challenging geometrical and arithmetical puzzles, many with solutions. - http://puzzlemochalov.com/

SMSU Problem Corner - Math challenges Southwest Missouri State University in three levels of difficulties. - http://math.missouristate.edu/~les/POTW.html

Polyhedra Links - Pastime and activity links for various geometric patterns, polygons and polyhedra by Jill Britton. - http://britton.disted.camosun.bc.ca/jbpolyhedra.htm

Puzzle of the Week Archives - A collection of puzzles, with hints and full solutions. Compiled by George Moody. - http://ecg.mit.edu/george/puzzles/

Mathproblems.info - Over one hundred and fifty math problems ranging from basic math to differential equations. - http://mathproblems.info/

Storkey: Two Envelope Paradox - A tough but simply defined problem which demonstrates key issues in probability. - http://www.anc.ed.ac.uk/~amos/doubleswap.html

Aha! Puzzles - Puzzles, books, games and tests with designed by Lloyd King, author of "Test Your Creative Thinking". - http://www.ahapuzzles.com

Free Puzzle Collections - Educational and recreational puzzles for teachers, students and parents. Each puzzle is graded by difficulty and has a hint. Solutions are available to members. - http://www.freepuzzles.com/

Algebraic Math Puzzles - A collection of puzzles at high school level. Does not include answers. - http://www.lifesmith.com/mathpuz1.html

Mathpuzzle.com - Celebrates math puzzles and mathematical recreations. - http://www.mathpuzzle.com/

Alphametics and Cryptarithms - Puzzles in which letters or symbols are substituted for the digits in an arithmetical operation like addition. - http://www.mathematik.uni-bielefeld.de/~sillke/PUZZLES/ALPHAMETIC/

Contest Center Cryptarithms - Examples of cryptarithms, with prize competitions for subscribers. - http://www.contestcen.com/rithms.htm

Sequence Puzzles and Problems - With links to related sites. Compiled by Torsten Sillke. - http://www.mathematik.uni-bielefeld.de/~sillke/SEQUENCES/

Scott Kim - Puzzles for web, computers, and print; ambigrams. - http://www.scottkim.com/

Alphametic Puzzles - Numerous puzzles, links, puzzle solver, and a generator. - http://www.tkcs-collins.com/truman/alphamet/

Alien Tiles - Object of puzzle is to try to get color pieces to create certain patterns in cube. - http://www.alientiles.com/

Math Puzzles - Logic puzzles and riddles with some solutions. - http://www.math.utah.edu/~cherk/puzzles.html

Torus and Klein Bottle Games - Collection of Java-based educational puzzles. - http://www.geometrygames.org/TorusGames/index.html

15 Puzzle of Sam Lloyd - Play online Sam Lloyd's "15" puzzle. The funny story and mathematical implications of this game. Some funny logical problems with the 15 game. - http://www.holotronix.com/samlloyd15.php

The Contest Center - Classic puzzles and riddles requiring only simple logic and elementary math. - http://www.contestcen.com/classic.htm

Paul Hsieh's Puzzles - Logical and mathematical brain teasers, with an indication of difficulty. Hints are provided; solutions are available by email. - http://www.azillionmonkeys.com/qed/puzzles.html

Nick's Mathematical Puzzles - A collection of puzzles, with hints, solutions, and links to related mathematical topics. - http://www.qbyte.org/puzzles/

Mathematical Recreations - Detailed exploration of a selection of mathematical topics. - http://www.mathrec.org/

Wu's Riddles - A collection of riddles, puzzles, and technical interview questions, with a discussion forum. - http://www.ocf.berkeley.edu/~wwu/riddles/intro.shtml

Mixed Up Math - Logic problems, where equations are mixed up. In various formats like boxes, crosses, diagonals, mazes. Free download. - http://www.kprobe.com/kprobe/mu.htm

Perfect Times - Teaches and assesses fluency of multiplication and division tables using online cards. Submit data and compare results. - http://www.perfect-times.co.uk/

Polymorf - Symmetry of Polyhedra - A demonstration of the symmetry and transformational properties of the Platonic and Archimedean solids. - http://www.polymorf.net/

Logicville - Educational puzzles, brain teasers, and word games such as anagrams, cryptograms, alphametics, doublets, tangrams. - http://www.logicville.com/

Brain Teasers and Maths Puzzles - Interactive logical and mathematical puzzles with feedback and detailed solutions. - http://www.syvum.com/teasers/

Mathschallenge.net - A website dedicated to the puzzling world of mathematics, with a discussion forum. - http://mathschallenge.net/

Archive Creative puzzles - Interactive puzzle archive with descriptions for puzzle construction and a special childrens puzzle page. - http://www.creativepuzzels.nl

Mathwizz - Interactive math problems for abilities ranging from middle school to university. - http://www.mathwizz.com/

Pythabacus - Description and instruction of using the ancient Pythagorean Abacus to do arithmetic. - http://www.pythabacus.com/

Colorful Mathematics - Educational software presents advanced mathematics to K-12 students in a game-oriented approach, using coloring and drawing techniques to illustrate concepts from graph theory and computer science. - http://www.math.ucalgary.ca/~laf/colorful/colorful.html

A+ Math - Interactive math help for K-12 students with flashcards, Math Wordfind, Homework Helper and worksheets. - http://www.aplusmath.com/