Plastic Containers: Storage containers with lids can be great building blocks and they also come in a variety of shapes and sizes. Children will enjoy trying to mix and match the lids or be amused that they can store items in the bricks of their building. Plastic containers come in a variety of sizes and shapes and are easy to stack inside of each other when playtime is over.
Empty food containers: Plastic containers that food has come in (such as sour cream, butter or cottage cheese) can be great building blocks. Save the lids and wash containers thoroughly and then decorate by taping pictures, stickers or using contact paper. Empty cylinder canisters that chips or oatmeal come in can also be great fun and decorated in a variety of ways. Soda bottles are not stackable but can be added to the top of structures for decoration (for example, a soda bottle can become the top of a castle). If filled with colored tissue paper they can be a real decorative feature. Other items to try are metal or plastic coffee cans with lids (beware of sharp edges on the metal), egg cartons and cardboard milk cartons. The tops of milk cartons can be folded down and taped to make the carton square all over for easy stacking.
Styrofoam blocks or packing peanuts: Many boxed items purchased from a store come with Styrofoam blocks for packing purposes. These can make interesting and fun blocks because they come in a variety of shapes. Packing peanuts are not stackable but with a box of toothpicks a child can make many wonderful sculptures by sticking Styrofoam together with the toothpicks.
Wood Scraps: If you know someone who does woodworking ask them to save the wood scraps for you, or check with your local lumber yard to see if they have scraps. Wood scraps should be sanded to avoid splinters. For older children a hammer and nails can be provided to make permanent structures. If using tools children should be supervised by a responsible adult.
Thread spools: Save the spools that sewing thread comes on. Because of their size they can easily be stored away in a container and are easy to grasp for small hands. Spools also come in different sizes and young children should be supervised because they may be a choking hazard.
Shells: Seashells can easily be obtained if you live near the ocean or know someone who is visiting the ocean. But, shells can also be purchased in most craft departments of stores. They are not as stackable as the other items, but can be used to outline buildings or where a driveway or sidewalk is or be placed on the top of the constructions for a decorative touch.
If combinations of all these ideas are used children will have building blocks that greatly vary in texture, size and shape. These blocks can be used for building forts for themselves or homes for their dolls/action figures, letters can be added for spelling fun or features like windows, doors or body parts can be drawn onto the blocks. A child will be limited only by their imagination.