Band-aids

Batteries (car, alkaline, NiMH, NiCad)

Books

Bottle tops (metal or plastic)

Bottles (plastic or glass)

Boxes (cardboard)

Branches (large, up to 20cm diameter each and 1.5m long)

Branches (small, up to 7.5cm diameter)

Bread bags (plastic)

Bubble wrap

Bricks or rubble/building materials