Corrugated cardboard (has ridges) can be recycled with your regular recycling program. Most transfer stations  require that you flatten the cardboard (i.e. break down the boxes).

 

Boxboard is a type of carton which is gray or brown when ripped. Examples of recyclable boxboard are cereal boxes (remove the plastic or waxed paper bags from the inside), pasta boxes (remove plastic windows), cracker boxes and tubes from toilet paper and paper towels. Boxboard can be recycled at all District transfer stations (except Cavendish).

EXCEPTIONS: Containers used in your refrigerator or freezer (like six-pack and soda boxes, or frozen food boxes) are not recyclable, due to the "wet-strength" additive which keeps the box from falling apart. Also, boxes which are white inside when ripped (e.g. those from Dunkin' Donuts) are not recycled with boxboard.  They should be added to the mixed paper collection.