Brain Teasers

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

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

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

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

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

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

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

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

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

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

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/

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

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/

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

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

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

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

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

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

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

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/

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

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

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

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

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

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

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

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

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

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

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

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/

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

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

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

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

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

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

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

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

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