Although still a work-in-progress, this device by Instructables user "TheSteamer71" is a great demonstration of what's possible with an Arduino and some imagination. They've created a robotic, multi-jointed arm that is controlled by several servos via the Arduino. Then various movements are a simple matter of the right sequence of commands to the servos. When making your own version, be sure to use high-torque servos and power them from an independent power supply, not the Arduino itself. And here's the ARM in action:
If you'd like to learn about Arduino - but not sure how to start - then the best way to learn is with our Experimenter's Kit for Arduino:
The package includes a wide variety of parts, sensors and modules including: a servo motor, lights, buttons, switches, sound, sensors, breadboard, wires and more. Furthermore a Freetronics Eleven Arduino-compatible board is included to make this an extensive hobby experimenter, inventor and starter kit. However we don't leave you alone to figure it all out, included is a great project and instruction booklet, plus access to a supporting web page and software examples. In other words - this is everything you need to get started for a fun range of electronics and Arduino related projects!
So to get started or for more information and to order, check out the product page.