Scott Kim

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

Logicville

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

Interactive Mathematics Miscellany and Puzzles

Java-based math resource including articles, puzzles and links.
http://www.cut-the-knot.com/content.html

A+ Math

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

Pythabacus

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

Mathwizz

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

Archive Creative puzzles

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

MatheMagic

A collection of mathematical puzzles, jokes and articles.
http://geocities.com/mathimoh

Mathschallenge.net

A website dedicated to the puzzling world of mathematics and computer programming.
http://mathschallenge.net/

Math Forum

Resources, problems and forum for teachers and students in mathematics.
http://mathforum.org/

Brain Teasers and Maths Puzzles

Interactive logical and mathematical puzzles with feedback and detailed solutions.
http://www.syvum.com/teasers/

MatheMajik

Indian site featuring calculation tricks and math puzzles.
http://mathemajik.tripod.com/

Polymorf - Symmetry of Polyhedra

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

iQED!

Lateral puzzles from "Puzzles for the High IQ" author Lloyd King and founder of The Puzzle Wizards SiteRing.
http://homepage.ntlworld.com/atalanta

Mr Titen's More Than Math

Mathematics teacher provides puzzles for students.
http://www.geocities.com/EnchantedForest/Tower/1133/

The Puzzling World of Barry R. Clarke

Brain teasers, articles and puzzles forum.
http://barryispuzzled.com/

Tile Tris

Tile a spheroid working room aperiodically or periodically. Includes free demo download.
http://members.lycos.co.uk/tiletris/

Brain Teasers by QBrute

Original brain teasers with solutions.
http://www.angelfire.com/empire/qbrute/

Magic Math Kingdom

Learn math through games and quiz-oriented tutorial.
http://www.nes-lab.com/english2/

The Enigmatic World of Philip Carter

Collection of brain teasers from the author of IQ books.
http://www.knowl.demon.co.uk/

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/

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

The Null Set

Puzzles collected by Guy Kindler, most requiring some undergraduate mathematical knowledge. Some hints are provided.
http://www.princeton.edu/~mathclub/puzzles.html

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

Mathematical Recreations

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

Nick's Mathematical Puzzles

A collection of puzzles, with hints, solutions, and links to related mathematical topics.
http://www.qbyte.org/puzzles/

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

The Contest Center

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

15 Puzzle of Sam Lloyd

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

Torus and Klein Bottle Games

Collection of Java-based educational puzzles.
http://www.geometrygames.org/TorusGames/index.html

SMSU Problem Corner

Math challenges Southwest Missouri State University in three levels of difficulties.
http://math.smsu.edu/%7Eles/POTW.html

BCIT Mathematical Entertainment

Famous mathematical problems, puzzles, facts, games and trivia.
http://www.math.bcit.ca/entertainment/

Math Puzzles

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

Alien Tiles

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

Alphametic Puzzles

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

Sequence Puzzles and Problems

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

Clever Games for Clever People

Games that interest John Conway including Rim and Traffic Jam.
http://www.cs.uidaho.edu/%7Ecasey931/conway/games.html

Contest Center Cryptarithms

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

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/

Alphametics Page

Compiled by Mike Keith. Examples of various genres.
http://members.aol.com/s6sj7gt/mikealp.htm

Logic Puzzles

Collection of original numerical-logic puzzles. Many are long and difficult, involve sorting and comparing long lists and are intended to be solved using a good spreadsheet program.
http://www.geocities.com/bob_kraus_2000

A Primer on Cryptarithmetic

Instructions, examples, references and links.
http://www.geocities.com/Athens/Agora/2160/primer.html

Ken Duisenberg's Puzzle of the Week Archives

Challenging puzzles and problems.
http://www.ecst.csuchico.edu/%7Ekend/potw/archlist.html

Mathpuzzle.com

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

Algebraic Math Puzzles

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

Group Games

Animations that develop the theory behind such puzzles as the Rubik cube.
http://www.dsm.univ.trieste.it/%7Elogar/duek2/index_engl.html

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/

Aha! Puzzles

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

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

Mathproblems.info

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

Nick's Mathematical Puzzles

A collection of puzzles, with hints, solutions, and links to related mathematical topics.
http://www.qbyte.org/puzzles/rss2.xml

Puzzle of the Week Archives

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

Curious Numbers

A tribute to the lighter side of math including puzzles, humor, trivia, quotes, inspirations, and math links.
http://www.geocities.com/mrsjennifercall/jennifer_math.htm

Polyhedra Links

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