The kitchen is one of the obvious and most used types of dramatic or pretend play.
I have our play kitchen stocked with pans, bowls, a wooden spoon, a towel, an old Everyday Food, and of course food. When I finish using a cardboard box in the kitchen I tape it shut and give it to my daughter. Examples of boxes in her kitchen are for cookies, Jello, crackers, taco seasoning (a favorite of my daughters), and noodles. I also gave her an old spice container that she uses all the time to "cook." It's a great way to pretend with items from her "real" world. I also like that it doesn't cost me anything and if she breaks them, we are not out any cost.
So, think twice before you throw something away. Can your child use it for pretend play?