Plastic Symbols

The SPI resin identification coding system is a set of symbols placed on plastics to identify the polymer type. It was developed by the Society of the Plastics Industry (SPI) in 1988, and is used internationally. The primary purpose of the codes is to allow efficient separation of different polymer types for recycling.

  PETE or PET 
Polyethylene terephthalate
Polyester fibres, thermoformed sheet, strapping, and soft drink bottles
  HDPE
High-density polyethylene
Bottles, grocery bags, milk jugs, recycling bins, agricultural pipe, base cups, car stops, playground equipment, and plastic lumber
  PVC or V
Polyvinyl chloride
Pipe, fencing, shower curtains, lawn chairs, non-food bottles and children's toys.
  LDPE
Low density polyethylene
Plastic bags, 6 pack rings, various containers, dispensing bottles, wash bottles, tubing, and various molded laboratory equipment
  PP
Polypropylene
Auto parts, industrial fibers, food containers, and dishware
  PS
Polystyrene
Desk accessories, cafeteria trays, plastic utensils, toys, video cassettes and cases, clamshell containers, packaging peanuts, and insulation board and other expanded polystyrene products (e.g., Styrofoam)
  OTHER or O
Other plastics, including acrylic, fiberglass, nylon, polycarbonate, and polylactic acid (a bioplastic), and multilayer combinations of different plastics
Bottles, plastic lumber applications, Headlight lenses, and safety shields/glasses.

Information from Wikipedia