diy "moon sand" 5 cups of regular flour and 1 cup of baby oil. simply mix the two together and it turns into this silky soft sand. you can throw some sand toys into your tray or you can use items such as spoons and measuring cups
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.
Such a fun homemade toy! Kids can move the boards to create all kinds of tracks for their toy cars! (How to Make Wooden Roads and Ramps for Toy Cars)~ Buggy and Buddy Just wood boards painted black with colored tape used as lane dividers.