Brain Teasers

Braingle - Brain Teasers & Riddles - Includes a huge collection of user submitted and rated brain teasers and riddles. It also has a lively message board and some unique multiplayer games.
http://www.braingle.com/

Eyetricks: Brain Teasers - Weekly puzzles and archives.
http://www.eyetricks.com/brainteasers/

Bill's Brain Teasers - A collection of visual and linguistic riddles.
http://www.billsgames.com/brain-teasers/

Zuzzle Puzzles - Collection of puzzles including riddles, logic puzzles and sequential puzzles.
http://www.zuzzle.com/

A Game A Day - A puzzle site featuring a new puzzle format each weekday for each month. Puzzles are fun, educational, entertaining and are also printable.
http://www.agameaday.com

Just Riddles and More - Riddles, illusions, puzzles, and brain teasers.
http://www.justriddlesandmore.com

Puzzle Contest Center - Riddles, brainteasers, cryptograms, anagrams, and logic puzzles. Compete in eight new contests monthly.
http://www.contestcen.com/

AVAV - Collection of optical illusions, brain teasers and riddles.
http://www.askix.com/avav/

Rec.puzzles Archive - An archive of many popular puzzles from the rec.puzzles newsgroup.
http://rec-puzzles.org/

Had To Play On - A community based site with competitions, challenges, awards, a help centre, forums and games.
http://www.hadtoplayon.com

National Puzzlers' League - Crosswords and other word puzzles and games, samples; monthly puzzle magazine; 800,000 word searchable list.
http://www.puzzlers.org/

BrainBall - A daily brain puzzle with 10 different tasks and a variety of statistics on your performance.
http://brainball.playwithyourmind.com/

BrainBashers - Brain teasers, puzzles, riddles, games and optical illusions.
http://www.brainbashers.com/

Brain Teaser World - Offers riddles, puzzles, optical illusions, and magic tricks.
http://www.brainteaser-world.com/

Brain Juice - An assortment of entertaining logic puzzles with solutions and indicated levels of difficulties.
http://www.brainj.net/puzzleindex.php

Curiouser.co.uk - Paradoxes, puzzles, games, optical illusions, poetry, curious facts, and quotations.
http://www.curiouser.co.uk

Word Juxtapoz - Word puzzles, riddles, rebuses, brain teasers, mazes, cliparts and pictures.
http://www.wordjuxtapoz.com/

Professor Tangent - Have fun with games, puzzles, brainteasers and humor as you learn about logic and analysis.
http://www.professortangent.org

Pzzls - A collection of logic puzzles, riddles and brain teasers.
http://www.pzzls.com

The Stone - an online mystery game. Hours of clever puzzles and riddles. Puzzles challenge the mind of serious and amateur players worldwide.
http://www.thestone.com

The Amazing Art Site - Huge collection of optical illusions, hidden imagery, ambiguous art and upside downs.
http://members.lycos.nl/amazingart/

Brain Teasers - Brain teasers, riddles, logic puzzles and problems, paradoxes, optical illusions, IQ tests and logical games.
http://brainden.com/

Thinking Game Forums - Chat and discussion about online thinking games.
http://www.infordigital.com/

Archimedes' Laboratory - Recreational mathematics including puzzles to make and solve, tessellations, geometric puzzles, optical illusions, and curiosities.
http://www.archimedes-lab.org

Unitix Entertainment - Online games, puzzles and other interactive brainteasers. Fun for all ages.
http://unitix.com/entertainment

The Grey Labyrinth - A beautifully illustrated collection of puzzles, riddles, and paradoxes. Features a changing "unsolved puzzle" plus three years worth of previous puzzles.
http://www.greylabyrinth.com/

The Logic Zone - Collection of problems with answers, logic puzzles and cryptograms.
http://myweb.tiscali.co.uk/thelogiczone/

Abnorm's Conundrums - Easy, medium and difficult brain teasers without answers.
http://www.angelfire.com/oh/abnorm/

Thinks.com - Recreations for active minds including games, puzzles, math, words, images, books, software and web guide.
http://www.thinks.com/

PedagoNet Brainers - Over 60 brain teasers to enhance your mind.
http://www.pedagonet.com/brain/brainers.html

All-Star Puzzles: Logic Problems - Collection of logic problems to solve. Printable.
http://www.allstarpuzzles.com/logic/

Gray Watson's Brain Teasers and Riddles - A collection of brain teasers and riddles with a guess button.
http://256.com/gray/teasers/

Planetarium - An on-line puzzle story in twelve weekly installments.
http://www.beholder.co.uk/planetarium

Roh'El's Riddles - Offers brainteasers rated by difficulty and category.
http://users.telenet.be/jo.roel/Riddles/index.html

A Puzzlemakers Site - Puzzles of all descriptions.
http://www.puzzlemakers.net

iRIDDLER - Challenge your mind with free online riddles/puzzles, logic games, brain teasers and view optical illusions.
http://www.iriddler.com

Puzzles Without Rules - Free, updated, original abstract puzzles for advanced puzzle-solvers. Includes current unsolved puzzle and archive with hints and solutions.
http://puzzleswithoutrules.blogspot.com/

Eluzions - Featuring all sorts of games, optical illusions, puzzles, trivia, mazes, and magic tricks. Suitable for all ages.
http://eluzions.com/

Confusion - It's a challenge to reach the end of this puzzle maze.
http://cnfsn.tripod.com/

Say What You See! - Collection of visual brain teasers which can be solved by saying what you see.
http://www.eyetricks.com/swys/swys0101.htm

Able2Know - Message board of user submitted riddles and brain teasers.
http://able2know.com/forums/viewforum.php?f=8

Puzzability - Some real mind benders here.
http://www.puzzability.com/

BrainVista - Collection of solved and unsolved brain teasers.
http://www.brainvista.com

Sesquip Word Games - Challenging word games published in newspapers.
http://www.sesquip.com

BrainBoggled.com - A collection of math, logic, and word puzzles.
http://www.brainboggled.com/