Shareware game based around an extension of the game of life.
IBM Research: Ponder This
Monthly logic and math puzzles set by IBM researchers with solutions.
Number puzzles with various levels of difficulty and solutions. Includes printable versions.
Monty Hall Game
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.
Quick Logic Puzzles
Use the clues provided to deduce the correct sequence of numbers in the hidden code.
The Monty Hall Problem
A probability theory puzzle with solutions. [English and German.]
Two Envelope Paradox - Solution
Claims that the two envelope paradox comes from the incorrect use of probabilities.
Discussion board hosted at Berkeley with talk about a variety of solved and unsolved brain teasers.