Just about everyone has now seen Sudoku, but there are another dozen similar and fun puzzles that teach even more math skills. You can find many free versions of these puzzles on the web at http://www.mathinenglish.com/index.php or other sites on the web.
Here are some to get you started (From: http://www.mathinenglish.com/index.php)
Ken-Ken is terrific! There are even books of KenKen puzzles in the US that you can purchase.
Rules For Playing KenKen®
The numbers you use in a KenKen puzzle depend on the size of the grid you choose. A 3 x 3 grid (3 squares across, 3 squares down) means you use the numbers 1, 2, and 3. In a 4 x 4 grid, use numbers 1 to 4. A 5x5 grid requires you use the numbers 1 to 5, and so on.
The numbers in each heavily outlined set of squares, called cages, must combine (in any order) to produce the target number in the top corner using the mathematic operation indicated (+, -, ×, ÷).
Here's how you play:
1. Use each number only once per row, once per column.
2. Cages with just one square should be filled in with the target number in the top corner.
3. A number can be repeated within a cage as long as it is not in the same row or column.
That's it! Can you solve the sample above?
Kakuro From: http://www.mathinenglish.com/index.php
Each grid has horizontal and vertical lines containing either clues or empty cells. The clue number is the sum of the empty cells it represents. These clues are printed either above a diagonal line or below a diagonal line.
If the clue is printed above the line, the clues is the sum of the empty cells to the right. When the clue is printed below the line, it is meant for the row of empty cells below the clue number. Each number between 1 and 9 can only be filled in once! So when the clue says 4, and there are 2 empty cells, you cannot fill in 2 and 2. The answer must automatically be 1 and 3.
What is Shikaku or Rectangles ?
Sikaku is all about the areas of squares and rectangles. The player has to fill a grid with rectangles or squares with areas of already printed numbers. When an 'eight' is printed in the puzzle the player has to figure out whether to draw a '8 by 1' rectangle or a '2 by 4' rectangle. When a 'nine' is given, a '3 by 3' or '9 by 1' rectangle/square must be filled in.
The areas of prime numbers are easier! A 'thirteen' printed in the grid can only mean a rectangle of '13 by 1'! The more clues in the puzzle, the easier it is to solve. The difficult Rectangle puzzles contain no clues at all! Use your logic skills to do the math!
Fubuki (like magic squares)
What is Fubuki? http://www.mathinenglish.com/Fubuki.php
Fubuki is and great math game, or number puzzle, in which your addition and multiplication skills are needed. Each puzzle consists of a 3 by 3 grid which has to be filled with the numbers 1 to 9. Each number can and must be used only once and, in case of the addition Fubuki, add up to the totals of each horizontal or vertical row or column of 3 numbers. In the case of the multiplication Fubuki, the 3 numbers are the multiples of the given products. The rules of this maths game are pretty simple, but solving these puzzles is another story. Brain training to the max!