Available puzzles include traditional pencil-and-paper puzzles with online Java applets for solving, such as word searches, plus there are cryptograms, logic problems, memory games, and more.
http://www.allstarpuzzles.com
Explore the fascinating world of logic puzzles -- online or with pencil and paper. Learn everything about number logic and picture logic puzzles from the world's leading logic puzzle source.
http://www.conceptispuzzles.com/
With a high degree of difficulty, these puzzles are challenging. That can, however, be very fun. In case one becomes stuck on a puzzle, there is a discussion forum for players.
http://www.greylabyrinth.com/
Optical illusions to trick your and entertain your eyes, brain games.
http://www.optillusions.com/
Many puzzles to choose from, including analysis, combinatorics, cryptology, geometry, language, logic, trivia and more.
http://rec-puzzles.org/
A site for technical interview questions, brain teasers, puzzles, quizzles and other things that make you think!
http://www.techinterview.org/
Free sudoku site that gives a player their choice of puzzle difficulty and even shows players how well they are doing on a particular puzzle.
http://www.websudoku.com/
There are all kinds of word games and word puzzles to enjoy. All the unique and addictive word games you could possibly want, all in one place.
http://www.word-game-world.com/
Online puzzle magazine committed to giving solvers free, daily-updated logic, crossword, and cryptic puzzles.
http://crpuzzles.com/
Enjoy 32,400 free online crossword puzzles. Site also features a puzzle maker and helper.
http://www.crosswordpuzzlegames.com/