I've had lots of people ask me about the sandwich and snack bags that I send in the children's lunch boxes. They are called Happy-sacks, and I cannot recommend them enough. They are cloth on the outside and a wipeable nylon on the inside. They come in a variety of sizes and are machine washable. We usually just wipe them out. They save on waste and money (you don't have to buy bags anymore!). In short, we love them!
Obviously there is much more we can do in our family to positively impact the earth, but I feel like these bags are a step in the right direction.