The Free Universal Construction Kit is an innovative new product that lets you combine pieces of building toys such as LEGO, K'Nex, Tinkertoys, Zoob, Duplo, etc., thereby allowing your creative mind to run free.
Even better than the rock solid design of the adapters is the fact that the Universal Construction Kit is free to download and print via 3d printer. I'm not sure how much 3d printing costs, but the pieces are pretty tiny so it shouldn't be too expensive, right? *sheepish grin*
Link --via Geekologie