Polystyrene
Polystyrene foam, or PS, is commonly refereed to as Styrofoam, but this is actually a brand name of the Dow company. Polystyrene, with the chasing arrows symbol number six, is used for packing peanuts, meat trays, warm beverage cups, padded packaging as well as the foam facet of foam core. It is not an easily recycled plastic.
Traditional Foam Board
Polystyrene is more often reused than actually recycled. Very few community recycling programs accept foam, but you can ask your solid waste district if there are special drop-off days in your region. Your municipal recycling program may also know of local places, such as shipping companies, that accept it for reuse. You will need to remove the cardboard lining prior to recycling. Also, there are a number of mail-back programs to recycle polystyrene foam.
Greening Foam Board
There are many brands and varieties of foam board, some more eco-friendly than others. Look for thermoplastic foam core along with brands made with wood fiber. Always use as little foam board as possible and try to reuse it.