Truffle-Swine Keeper - A minesweeper clone that contains 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
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
Bomb Hunter - Commercial mobile-phone version of Minesweeper with new tools including probes and a radar. - http://www.airplayuk.com/games/bombhunter/
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/
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 - Contains advice, cheats, rankings, downloads, and a forum. [English and French.] - http://www.planet-minesweeper.com/
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
The Minesweeper Handbook - This handbook teaches how to play better Minesweeper, taking you from the fundamentals through to advanced concepts. - http://www.minesweepers.org
Writings on Minesweeper - Contains various articles on Microsoft's Minesweeper including randomness, board cycles, first click, and bugs. Extensive experimentation. - http://www.nuprograms.com/minesweeper/
Hexatron - Variation of Minesweeper with hexagonal grid. Java applet. - http://www.hexatron.com/hex/
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
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/
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/
#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/
Programmer's Minesweeper - Java applet for testing computer strategies for playing minesweeper. - http://www.ccs.neu.edu/home/ramsdell/pgms/
Dynamite Minesweeper (Dynamine) - A more continuous variation on minesweeper. Free Windows 3.1 implementation. - http://www.alumni.caltech.edu/~manning/dynamine.html