Most 3D printers create three-dimensional objects by adding layers of a material to a surface. They work like hot glue guns, forming patterns layer by layer until the objects are fully formed. For a review of consumer models, see Make’s Ultimate Guide to 3D Printing 2014.
Aabriti made this iPad stand using Sketch It Make It. The project teaches design on a straight line, negative space, angles, and prototyping. You'll need an iPad and the free Sketch It Make It app, plus access to a 3D printer. If you don't have one, you can send your file to a service like Shapeways.
Named after the designer at Carnegie Mellon University, The Jessica Puzzle Kit is really fun for kids and adults alike. Design and laser-cut the geometric shapes, which notch together with right angles, parallel lines, and specific dimensions. You'll need an iPad and the free Sketch It Make It app, plus access to a laser cutter. If you don't have one, you can send your file to a service like Ponoko.