How to keep a child busy for hours in the summer: DIY: Giant Ice Cube Awesomeness - filled with plastic animals, dinos, and such. And I'm sure you could put in food dye before its frozen to color it like the ice block in the photo.
Lego Fraction game: Love this example for students who are into Legos. This is a great way for students to learn commonly used fractions in an exciting way. It supports the NCTM standard of representing commonly used fractions.
Rainy days:Brassy Apple: DIY laser maze kids activity using crepe paper! You would be surprised how easily kids get in awe when u create a unique fun game at home for them.plus this saves you all the dollars you would be spending at the arcade.