Nim
http://www.thisiscool.com/nim.htm
This applet simulates the original Nim game. You and the computer take turns removing objects from the rows; whoever removes the last object wins. There are many versions of Nim available, so you can use your favourite search engine to find variations on this game.

3-D Noughts and Crosses
http://web.ukonline.co.uk/arthur.vause/ThreeDoxo.html
A three-dimensional version of the popular game tick-tack-toe. To make it more difficult, there are four layers and each layer has a 4 by 4 grid. Use this game to improve your ability to think in three dimensions.

Set Game
http://www.reed.edu/~mcphailb/applets/set/
This card game may seem simple at first, but it will surprise you. The items shown on the cards have four attributes-colour, shape, number, and shading. You are given a subset of 12 cards from the deck of 81. To score points, you must find three cards that are either all alike or all different within each of the four categories. Mentally juggling all four categories is more challenging than it sounds! Help is provided for novice players.

The Factor Game
http://illuminations.nctm.org/tools/tool_detail.aspx?id=12
How well do you know the factors of numbers from 1 to 100? Take turns (with another player or the computer) identifying the factors of a number chosen by your opponent. The game ends when there are no more numbers and factors to select. The winner is the player with the greatest sum. Play a few times to develop a strategy!

Java Maze
http://www.falstad.com/maze/
Java Maze gives you a tunnel view of a maze from which you must escape. Use the arrow keys to move around in the maze. If you wander around long enough, you will eventually escape, but to find the exit quickly you need to do some data recording and analysis.

Sprouts
http://www.math.utah.edu/~alfeld/Sprouts/
This is a game for two players. Take turns drawing curves between any two dots. The player who draws the last possible curve wins. The challenge is that the curves must not intersect, and no more than three curves may come from any dot.

Knot Funny
http://javaboutique.internet.com/KnotFunny/
Knot Funny challenges you to unscramble 16 numbers in a 4 by 4 grid. The catch is that you can't move individual squares; you have to work with a block of numbers at a time. Although it looks simple, unravelling the scramble will test your patterning skills.

Safebreaker
http://www.pimpernel.com/safe/
The object of this game is to break the five-digit code in the fewest number of trials. After each trial, the computer gives you feedback on which digits are not in the code; which digits are in the code but in the wrong place; and which digits you have identified correctly.

Math Hangman
http://www.nj.devry.edu/~rhadley/hangman/mathhangman.html
Guess the letters in the words or phrases selected by the computer before you run out of moves. The words are quite challenging. So, this game will stretch your knowledge and your vocabulary.

Rubik's Illusion
http://www.dotsphinx.com/games/rubik/illusion/
Your goal: get five of your pieces in a row on this 8 by 4 grid before the computer does. The catch: there's a mirror that doubles the number of squares and doubles each move. There are six levels of difficulty.

Daleks
http://www.koobifora.com/daleks/
This game is based on an old science fiction television series called Dr. Who. Several Daleks (evil robots) are trying to catch Dr. Who, and your task is to help him escape. To win, you'll need your knowledge of two-dimensional geometry, logical thinking, and planning skills.