We all love cardboard. It's such a versatile and creative material. Our friends over at the Cardboard Collective are hosting their first ever cardboard challenge!
I think it's a great way to get your kids creative juices flowing! Check out the Cardboard Collective for more details!
Also The Imagination Foundation (remember Cain's Arcade) is hosting the first ever Global Cardboard Challenge on October 6th encouraging a day of play. You can look on their site to see if there is an event in your area. I love The Imagination Foundation's mission to find, foster, and fund creativity and entrepreneurship in kids. Check out their site for more info on that.
Here are some awesome cardboard costumes for some inspiration
Samurai from Instructables
A tractor from Coolest Homemade Costumes
LEGO brick from Country Living
Darth Vader from Costume Pop
An iPod from LilSugar
Or a battery from Costume Works