This is a two player game. The two players choose the total. Two numbers appear. If they add to the total, the first player to press their key gets a point. Three thumbs up!

http://www.oswego.org/ocsd-web/games/ghostblasters2/gb2nores.html

Choose your starting number. Then click repeatedly on only those ghosts which are multiples of that number. How long does it take to reach 100?
Three thumbs up!

http://www.oswego.org/ocsd-web/games/Ghostblasters1/gbcd.html

Play a "Connect-Four" style game, earning a game piece each time you answer an estimation question correctly. This game asks the players to estimate the answer to addition, multiplication, and percentage questions. Choose difficulty level, question types, and time limit. Estimator Four is one of the Interactivate assessment games.
http://www.shodor.org/interactivate/activities/EstimatorFour/

Here is a similar interactivity that doesn't have the Connect Four interface.

Estimator Quiz
http://www.shodor.org/interactivate/activities/EstimatorQuiz/

In this interactivity, you can choose 'Counting' where the students have to estimate the number of stars.

Estimator
http://www.shodor.org/interactivate/activities/Estimator/

More or Less Estimator
Is the number of objects more or less than the given estimate?
http://www.shodor.org/interactivate/activities/MoreOrLessEstimator/

Arithmetic Four is a Connect Four variation where you have to answer an arithmetic question correctly before you can play a chip. You get to choose the category, the operation, the difficulty level and the time limit.

http://www.shodor.org/interactivate/activities/ArithmeticFour/?version=1....

Arithmetic Quiz is similar but without the Connect Four interface.

http://www.shodor.org/interactivate/activities/ArithmeticQuiz/

Ancient Egyptians knew fractions like 1/2 or 1/4 ((one piece of a pie).
But to make fractions like 3/4, they had to add pieces of pies like 1/2 + 1/4 = 3/4.

For some reason, they never repeated the same fraction when adding; ie they never wrote: 1/4 + 1/4 + 1/4 = 3/4

This website presents a range of Egyptian maths problems for you to solve. Good luck!

http://www.mathcats.com/explore/oldegyptianfractions.html

Place all the numbers from 1 to 6 in the circles along the sides of the triangle (one number per circle), so that three numbers on each side add up to the same total - a magic sum.

There are four different magic sums that could be reached for this puzzle. All these sums are from 9-12 number range. Can you find all of them?

http://www.puzzles.com/PuzzlePlayground/MagicTriangle3X/MagicTriangle3X....

Here is the PDF version for the classroom.

http://www.puzzles.com/PuzzlePlayground/MagicTriangle3X/MagicTriangle3XP...

This is a game for all you Big Spenders out there.

I will give you a sum of money and all you have to do is spend as much of it as you can aren't I generous?!

Your aim is to get as many items as you can and be left with the least amount of change.

Notes:
* The money is is English pounds, but that isn't a major issue
* You will need the Shockwave plug-in, available from the website.

http://www.channel4learning.net/sites/puzzlemaths/shop.shtml

You have to fill in the missing numbers in the equations to stop Harvey being catapulted into the distance. Simply click on a number to select it.

There are four ropes holding the catapult down, so you've got four chances. You'll see the ropes snap if you choose a wrong number.

From some problems, even at level one, this game at times requires logical reasoning and good number skills. Or luck. I really love this game, but it is better I think for students who already have good number skills.

Notes:
* You will need the Shockwave plug-in for this game. It is available from the website.

http://www.channel4learning.net/sites/puzzlemaths/catapult.shtml

You have to find ways of using up to 4 numbers to match a target number exactly.

You don't have to use all the numbers - but you can use each number only once.

You can add, subtract, multiply, divide and even put them together.

Each level will vary the number of signs you can use and the choice of digits will be reduced to increase the difficulty.

Remember, there is always more than one way to reach the target number.

Notes
* You will need to have (or install) the free Shockwave Player.
* You can download the game from the website and run it as a stand-alone program

http://www.channel4learning.net/sites/puzzlemaths/make_it_count.shtml

This is a maths-based version of Pac-Man. You must eat the correct answer before the wrong answer eats you,
http://www.sheppardsoftware.com/mathgames/mathman/mathman.htm