The Arduino is a pretty straight-forward device: build a board with an Atmel AVR chip, voltage regulator, a USB serial port, offer a standardized way to interface with it via the use of 'shields', and provide a basic IDE (Integrated Development Environment) and standard set of libraries to talk to the device and tie it all together.

Normally, anyone doing this would get a reaction of a yawn as this pretty much describes a basic Atmel AVR development board. What makes the Arduino different from other microcontroller development platforms is that it also is:

• relatively inexpensive
• entirely open source (hardware and software)
• cross-platform (works on Windows, Mac, Linux)
• a platform that has achieved critical mass

The last item is important as it means that it's relatively easy to find someone else who has at least tried, and often succeeded, in trying virtually anything you can think of. As a result, there are a wide variety of add-on shields for circuits covering everything from LEDs and displays to Ethernet to motor control and more, pre-built libraries, schematics, how to's... you name it. This makes the Arduino a very productive platform for hardware hackers... once the basic environment is up and running, you can pretty much focus on the problem you are trying to solve or the specific area you want to learn about.

To quickly get started with the Arduino:

1. Download and install the USB serial port driver (Mac and Windows only as current Linux distros should have it installed already)
2. Download and install the Arduino IDE (which is based on Processing... it is not important to know this now, but I found it handy to understand this later when I was wondering why the IDE works the way it does.)
3. Connect your Arduino to the computer via USB
4. Tell the IDE which serial port to use via the Tools->Serial Port menu
5. Open up a program, called a sketch (File->Examples->Digital->Blink on the menu is a popular starting point)
6. Upload your sketch to the Arduino via the File->Upload menu (or upload shortcut icon in the sketch window)

At this point, you are pretty much done: the device is now doing whatever the sketch you uploaded told it to (in the case of the Blink demo, blinking the LED on the Arduino board.) Sketches are written in C++ but it's fairly lightweight C++ so if you know C, you should be able to pick it up the subset of C++ used pretty quickly. To wire up your own circuits down the road you probably also want either a full-sized breadboard or a protoshield with a mini breadboard. I have and use both depending on the size of the project I am working on and find they both have their uses.

Also, it is not strictly necessary that you have an Arduino brand board but I'd suggest starting with one as it ensures you are able to use 3rd party shields and makes it easier to get help if you have problems getting started. Once you're comfortable with it, and if you decide to branch out into more extensive projects, it will often make sense to go with 3rd party Arduino-compatible boards or make your own (I've done both for different projects) to save some money and/or get just the form factor you are looking for.