The Lunchopolis, by New Wave Enviro Products, is awesome. For only twenty bucks, you get an insulated lunch box, a beverage container, two small snack containers, and two larger containers which are good for sandwiches and whatnot.
While not as green as stainless steel food containers, they are BPA-free and reusable. They're also a lot cheaper than stainless steel options. They're sturdier than most inexpensive plastic containers and without a BPA plasticky smell.The bottle can also be filled with ice and used as an ice pack.
This lunch box set is great for kids or adults. And its nondescript designs make it "cool" even for older kids who may not want to carry around a lunchbox.
When putting the containers in your lunch box, make sure that the lid is completely on. Twice I thought the lid was securely on, but it wasn't, and I wound up with a mess in my purse. (I was carrying the containers filled with puffs in my purse for my tot) Don't make the same mistake that I made. (twice! :-))
I feel that one of the most important ways to help your kid go green is to send them to school with a waste-free lunch. Since this contains almost everything you need (throw in a cloth napkin and utensils) it will greatly reduce your waste. The Lunchopolis helps!