Jim Loy's Puzzle Page
Classic and original puzzles.

The Truth Tree's Math and Logic Board
Collection of math and logic puzzles ranging in levels of difficulty.

Dave's Logic Puzzles
Monthly logic puzzles with solving grids.

IBM Research: Ponder This
Monthly logic and math puzzles set by IBM researchers with solutions.

Leisure Ideas: Puzzles
Some mathematical puzzles with answers and/or a hint.

TechInterview
Answers to technical interview questions, programming problems, and brain teasers.

Perplexus
A forum and collection of brain teasers, logic problems, math problems, paradoxes, science games, probability, riddles, and geometric shapes. The puzzles are searchable and categorized, most have solutions.

The Monty Hall Problem
A probability theory puzzle with solutions. [English and German.]

CrocoPuzzle
Contains print-out and interactive versions. [English and German.]

Mathematical Jigsaw Puzzles
Information on polyominos and square puzzles.

The Eternity Puzzle
Article on how this difficult jigsaw puzzle was solved.

The Two-Envelope Paradox: A Complete Analysis?
Describes aspects of a critical problem and apparent paradox in probability theory.

WU Forums
Discussion board hosted at Berkeley with talk about a variety of solved and unsolved brain teasers.

Tangram Magic Egg
Tangram which creates hundreds of birds including geometry, tasks, solutions and downloads.

Two Envelope Paradox - Solution
Claims that the two envelope paradox comes from the incorrect use of probabilities.

Quick Logic Puzzles
Use the clues provided to deduce the correct sequence of numbers in the hidden code.

The Puzzles of Oscar
Contains puzzles and games with solutions.

Monty Hall Game
JavaScript example of the Monty Hall Game. This game demonstrates the real (empirical) affect of statistics. [Does not display correctly in all browsers.]

Leisure Ideas: Logic Puzzles
Some mathematical puzzles with answers and/or a hint.

CellFighter
Shareware game based around an extension of the game of life.