"Bisphenol A (BPA): BPAs are chemical compounds that are added to plastics to make them more durable; they're most commonly found in the linings of food containers, beverage cans, some baby bottles, and drinking bottles, and they can leach out into foods and liquids. Harmful side effects from consuming them can include increased risk of breast and prostate cancers, infertility, polycystic ovary syndrome (PCOS), and insulin resistance (which, in turn, can lead to type 2 diabetes). To be safe, store foods in glass containers, drink from stainless steel water bottles, and do your best to avoid canned foods."
The biggest no no is to warm up food in plastic with BPA in it. If you still have plastic tuperware that you are using to store your leftovers in, then consider getting a set of glass storage containers. You can find a nice set from Costco for only $15.
Update! My sister Julie went and bought a set yesterday and it was $30, but sometimes they have a coupon for $5 off. See her comments below. Still worth it!