In the July/August 2007 issue of Vegetarian Times Magazine they posted a very helpful breakdown of what those numbers mean on the bottom of plastic containers. I was surprised to discover that the organic Gerber baby food is in a number 7, which can't be recycled at all! This may make you reconsider some of the packaging of items that you currently buy.
1 : PET (Polyethylene Terephthalate)
Found In: Soft drink and water bottles.
Recycle rating: Excellent. Can be recycled into carpeting and fiber fillings for pillows, quilts and jackets. A large quantity is reused in the beverage market.
2: HDPE ( High-Density Polyethylene)
Found In: Milk Jugs, detergent bottles and trash bags
Recycle rating: Excellent. Can be reused in pipes, flowerpots and trash cans.
3. PVC (Polyvinyl Chloride)
Found In: Food wrap, cooking oil bottles, and "blister" packaging.
Recycle rating: Poor. Even though it can be reused in pipes, vinyl chloride has been classified as a carcinogen.
4. LDPE (Low-Density Polyethylene)
Found In: Grocery bags, garment bags, shrink wrap and squeeze bottles.
Recycle rating: Fair. Can be difficult to find centers that take this kind of plastic to be turned into trash bags, plastic tubing and plastic lumber.
5. PP (Polypropylene)
Found In: Yogurt containers, most bottle tops and some carpets
Recycle rating: Fair. Few centers accept PP. Can be recycled into battery casings, brooms and scrapers but can't be transformed beyond that.
6. PS (Polystyrene)
Found In: Plastic utensils, packing materials and Styrofoam.
Recycle rating: Fair. Can be recycled into egg cartons, concrete and insulation, but finding a recycling center to accept it is often difficult.
Found In: A wide variety of products; this usually refers to layered or mixed plastics.
Recycle rating: Poor. "7" plastics can't be recycled at all.