Minesweeper

The Authoritative Minesweeper
World records at all 3 levels, a few tips and cheats, and many links to software and related pages.
http://metanoodle.com/minesweeper/

Bomb Hunter
Commercial mobile-phone version of Minesweeper with new tools including probes and a radar.
http://www.airplayuk.com/games/bombhunter/

Crazy Minesweeper
Windows shareware implementation of Minesweeper and a new variation in which new types of mines contribute 2 or 3 to the number seen in adjacent squares.
http://www.astatix.com/crazyminesweeper.php

Dynamite Minesweeper (Dynamine)
A more continuous variation on minesweeper. Free Windows 3.1 implementation.
http://www.alumni.caltech.edu/~manning/dynamine.html

Hexatron
Variation of Minesweeper with hexagonal grid. Java applet.
http://www.hexatron.com/hex/

Lady Di's mines
Java Minesweeper dedicated to Diana Spencer, Princess of Wales and her campaign to ban landmines. Includes high scores.
http://www.minesweeper.org/

Mines-Perfect
An improved minesweeper-clone that generates guaranteed-to-be-solvable puzzles (never guess anymore) and has a Murphy's law option (guessing causes failure), more boards, sound, load, save, undo.
http://www.czeppi.de/english

#1 MineSweeper
Java implementation with three levels of play, and an online hall of fame, which requires two games with a low time to emphasize skill over luck.
http://www.mine-sweeper.com/

Minesweeper for Atari VCS 2600
Binary and source to a port of the Minesweeper game for the Atari VCS 2600.
http://soeren.informationstheater.de/atari/

The Minesweeper Handbook
This handbook teaches how to play better Minesweeper, taking you from the fundamentals through to advanced concepts.
http://www.minesweepers.org

MineSweeper3D
Windows implementation of minesweeper on the surface of a 3D polyhedron, with challenging new tilings, and many boards to choose from. World records maintained online using encrypted submission. Built-in auto-solver. Demo version available.
http://www.software3d.com/Mines3D/

Planet Minesweeper
Includes advice, cheats, rankings, downloads, and a forum. [English and French.]
http://www.planet-minesweeper.com/

Programmer's Minesweeper
Java applet for testing computer strategies for playing minesweeper.
http://www.ccs.neu.edu/home/ramsdell/pgms/

Richard Kaye's Minesweeper Page
Papers about the computational complexity of Minesweeper, namely that the usual game is NP-complete and that an infinite variation is Turing-complete.
http://web.mat.bham.ac.uk/R.W.Kaye/minesw/minesw.htm

Truffle-Swine Keeper
A minesweeper clone that includes an algorithm to compute the probability that a mine is under a certain field.
http://freenet-homepage.de/hskopp/swinekeeper.html

Wikipedia
Encyclopedia article on Minesweeper.
http://en.wikipedia.org/wiki/Minesweeper_%28computer_game%29