Calendar Math in the upper grades. Free recording sheet the students use (both 4th and 5th), plus an entire series to explain how to get it started in your class. Could maybe use this type of idea in my math classes as a constant review.
Math area and perimeter A game for 2 or 3 players. Each player chooses a colour pencil or texta they will use in the game. Players take turns rolling the dice, using the numbers that they rolled to draw the perimeter of a rectangle or square & writing the area in the middle of the shape. Game ends when players run out of room to draw. Winner is the player who has used the largest area/most squares.