Upcycling has become a hip buzzword in the continued effort to be more green, or earth conscious. According to Wikipedia, upcycling is "the process of converting waste materials or useless products into new materials or products of better quality or for better environmental value." Taking that into consideration, even toys can be made from what would otherwise be considered garbage.
Big Spring Environmental created a helpful list, complete with tutorials when required, of 20 toys you can make from trash. Some of the highlights on the list include a milk jug igloo that's large enough for children to play inside, a cardboard biplane, and a milk jug storm trooper helmet.
Another popular upcycling project is the art of creating children's play places from old furniture. Upcycle Us features a ton of really cool upcycling projects from everyday items, including children's play kitchen's and work benches made from cabinets and TV stands.
With these resources as a starting point there's no end to where your creativity and a full recycling bin can take you. Happy crafting.