3D Printed Toys
Wooden Toy Train to Duplo Bricks Adapter
Wooden toy trains (e.g. Brio trains) are great toys for kids and parents, but as soon as you start playing with them you want to build more fancy tracks. As we had many many duplo bricks laying around, a little adapter between the two systems needed to be designed (using the fabulous software FreeCAD) and 3D printed.
If you are interested, you can get them 3D printed at shapeways.