Cubify, a 3D printer company have just released the design files along with some instructions on how to build your own 3D printed quadcopter. The nice thing about this is that they have shared the STL files so you ont have to use one of the cubify 3D printers to make this. This looks like a rather cool quadcopter design although its rather basic, but if you have a 3D printer and are looking for something fun to build this weekend then this might give you something fun to build this weekend. And also you dont need to care too much about flying aggressively since if you crash it and break something then you just need to print another, with some exceptions being the propellers and possibly some of the RC gear. But still quite a fun project if you have some spare RC gear lying around.
You can find all the instructions along with a video and the STL files here