Arduino Uno R3 - Open Source Electronics Prototyping Platform

Arduino is an open sourced electronics prototyping platform. It is aimed at hobbiests, designers and artists - and therefore needs little technical knowledge to perform simple tasks.

The Arduino can be programmed to perform a task by connecting it to your PC and using the software found here. The programing language is simple and many examples can be found via a quick google. Once programed your Ardunio will perform the task you've set it until you reprogram it. It can be powered from a 7-12V DC source, this can be from an AC/DC unit or even a battery! The Uno gives you control over 13 digital and 6 analogue inputs or outputs to do with as you wish. What would you do with them? Here are some examples:

8 x 8 x 8 LED Cube

Robot Arm controlled by a Mouse

Low Earth Orbit Satelite

You might want to start with an easier application though, a series of easy tutorials can be found here

Links

Full Specifications (arduino.cc)
Getting Started Guide (arduino.cc)
Programming Reference (arduino.cc)
Arduino Forum (arduino.cc)
Phenoptix Forum (forums.phenoptix.com) 

Specs