3D printing and programming your own robot arm is a great way to learn about robots. The BCN3D MOVEO is a 3D printed robotic arm made using additive manufacturing technologies. It has an Arduino controller. This 5-axis robot is open source, so you can find its files on GitHub.
As you can see in this video, the robot arm can pick up and move items. You can program it to do a whole lot more.
[Source]