Open collaborative design/Virtual designs into physical objects

To be useful to anyone these designs need to turned into physical objects which unfortunately isn't quite as straightforward as compiling software or downloading it over the internet.
Ways to give these designs physical form range from getting your hands dirty and crafting it yourself to sending it, or at least parts of it, as an electronic file to a computer-controlled manufacturing system such as rapid prototyping or CNC machines that can accurately create parts in 3D in a variety of materials.