Ed Pegg, Jr.'s Math Puzzle of the Week

Puzzle Picnic

Sam Loyd's Puzzles (site by Tony Fatseas)

Puzzle Forum

Dan's Problem of the Week at dansmath.com

Justin's Puzzles

Wei-Hwa Huang's Puzzle Gadget

Eric Weisstein's World of Mathematics

Forsmarts Puzzles (biweekly puzzle competition)

Robert Abbott's Logic Mazes

Emerehan Halici's PuzzleUp Puzzles

PQRST Puzzle Competition (Cihan Altay's quarterly puzzle competition)

Puzzle Design Tournament (Cihan's yearly competition)

IBM's Ponder This

Turkzeka Puzzles

Puzzles of Leonid Mochalov

Brainteasers Network by Brent Guild

DapaMesa Puzzles

Puzzletome

Terry Stickels' Puzzles

Conceptis Logic Puzzles

Ján Adamovic's Brainteasers

Shepherd College's Problem of the Week

Southwest Missouri State University's Problem Corner

Andrea Gilbert's ClickMazes (very nice interactive mazes)

Brain teasers by Barry R. Clarke

Nick Hobson's Mathematical Puzzles

World of CryptoPics - Nonograms/Griddlers information and downloads

Dave Ellis's Puzzlets

Interactive Crosswords and Puzzles (with a good links page)

Internet Puzzle Solver's Test (Russia)

David Rock's Problem of the Week at Columbus State University

Lloyd King's Creative Puzzles

Everett Kaser Software

curiouser.co.uk

Frank Morgan's MAA Math Chat Column

The Contest Center's Math Page

Programming Puzzle Forum

Dave's Logic Puzzles

Macalester College Problems of the Week

Albert L. Delgado's Puzzle of the Week (Bradley Univ.)

Birmingham's Mathematics Puzzle of the Week

Daily Jumble Puzzles

Tim Edmonds' Primrose Puzzles Page

Jongmin Baeks' Math & Puzzles Page

Lateral Thinking Puzzles Forum

Math Forum's list of Puzzles of the Week

Geometry Forum: Problem of the Week

Geometry Forum: Project of the Month

20,000 Problems Under the Sea

Kevin Brown's Math Pages

Knot a Braid of [Math] Links

USA Mathematical Talent Search

Erich Friedman's Math Magic

All-Soviet-Union mathematical competitions 1961-1986

Uncle Bob (Mead)'s Puzzles

The Prime Problems and Puzzles Connection

Stephen Sproule's lists of Problems of the Week

Links to Cryptarithms

Dijit Consulting's Brainteaser

University of Louisville's "Reason Mathematically"

Puzzle sites hosted by John Rausch

Puzzle University

Thinks.com - 1001 uses for a playful brain

Panthera's Puzzle Contest

Yoogi Logic games and Puzzles

Cut The Knot's Puzzles

The rec.puzzles archive

The CarTalk Weekly Puzzler

The Case Weekly Mystery

amUous Mind Puzzles

Mathematics Problem Solving Task Centres

The Mathcad Puzzler

The Ultimate Puzzle Site

Aenigmatica (With link to English version)

NPR's Weekend Edition Sunday Puzzle

The Black Stump Puzzle Page

The Grey Labrynth

On-line Encyclopedia of Integer Sequences

Meriam-Webster Dictionary (you can search on wildcards like *dous)

Jumble and Crossword Solver

Dilbert's Daily Mental Workout

Mike Winckler's Puzzle of the Week

Sites that reference Ken Duisenberg's Puzzle of the Week

Trioker/Triominos Puzzles (French)

Web Wizard's Math Challenge

Slide Rule's Mind Games

The PCTM Puzzle of the Week

Chris Long's Think & Derive Page

Oriel D. Maxime's Homepage

James Cole's CraftyPuzzles (wooden brainteasers)

A dictionary of words (to search for letter combinations)