Uses:

Arts & Crafts
If you love crafts, there are a number of uses for cardboard. Lay it on your workspace to protect your floor or table when using particularly messy materials. If you are spray painting, remove the top and one side of a box. Set the item you are spraying inside of it so the box will act as a shield to prevent splatter. Paint on large, flat strips of it. Cut them into big, fun shapes, decorate them, and hang them on the wall. Put it together to make sculptures, models, and other decorations.

School
Corrugated cardboard sheets are perfect for dioramas or to create an inexpensive display board for a project. Teachers will find these display boards make excellent visual help in the classroom. When you’re done with one display for the year, all you have to do is fold it up and slide it into a storage closet to use again the following year. When it comes time for the school play, use corrugated cardboard to craft your props and scenery.

Gardening
Use it as a mulch to discourage weeds. Place a box over your tender seedlings to protect them from the hot midday summer sun or to shield them from strong winds. And if you find you’ve stockpiled more than you can use, shred it and put it into your compost bin.