The Yo-Yo itself is a metaphor for sustainable design. When you release the Yo-Yo with skill and care, it comes back allowing you to continue to enjoy the benefits over and over again, expelling little energy. If you just throw the thing out there with reckless abandon it'll get all tangled up into a big mess that just sits there taunting you and forcing you to expend time and energy to recover the little bastard and use it again.
It's fitting that Ben Floeter & Natalie Wright of "Suddenly, It's Real!" have created these sustainable Yo-Yos. Made from sustainably and locally harvested wood, they are hand made with natural shellac and 100% cotton string. To ensure quality, each one is rigorously tested by Ben himself.
Now I don't know how strictly these little guys adhere to the Cradle to Cradle principle, but they are definitely an earth friendlier option for those obsessed with the little instrument of rotational inertia. You can buy one of Ben & Natalie's creations at Fawn & Forrest.