From the arduino.cc website: "Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It's intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments." So what's that mean in plain english? Arduino is a little computer you can program using your PC or Mac. You send code to it that tells it what to do. Then you connect Electronic parts to it - like LEDs, buttons, sensors, switches, etc, and your code tells those things what to do. What can you make with it? All kinds of things! LED art is popular (see the charliecube link, below). Home automation systems (control your lights, heat, etc). Robots. There's very little limit to what you can do, if you're creative. It's a great way to learn electronics & coding combined, while actually making useful things.Basic LED connections
MAKE: Build a Makershield MAKE: Makershield Reference
I've found the Arduino cookbook by O'Reilly Press to be the best book... it's the only one I'd recommend buying at this point.
Here's a handy printable arduino pinout chart
Getting started in Arduino - there seems to be two schools of thought. 1 - buy a kit. 2 - buy an arduino & individual bits. My thoughts on each approach:
1 - buy a kit.
Has the advantage of getting lots of parts that go together, plus an arduino, to complete some basic tutorials. Adafruit, sparkfun, Make, and others all have starter kits. The downside here is they're expensive for what you get. I've already found the kit I purchased didn't have enough LEDs for most of what I want to do. Not enough resistors. The LCD is more basic than I want. No shift register for LEDs, etc. The thing is, I didn't know any of that before I bought it - I was just getting started in Electronics, after all! I didn't know what a shift register was!
2 - Source the bits from wholesale / ebay / fleamarkets
Has the advantage of price. You can get 100 RGB LEDs for $10 from Ebay, free shipping! That would be $170 at Radio Shack! The kit I bought had 3 RGB LEDs... not hard math. The downsides, for me, were obvious though. I didn't know what I needed, and shipping times would vary widely. I'm not a patient person - I didn't want an arduino here, but no LEDs for 3 - 4 weeks.
So the kit won out, for me. If you want to save money and have patience, research what's in the kit, and buy it elsewhere (links above!)
As another option, here's a "kit" I put together from Amazon & Adafruit - all the components of the common kits, in higher quantities. Getting Started Kit
Ok, so I have the stuff, now what?
Make an LED Blink
Make an LED Blink when I push a button
Make an RGB LED blink from red to green to blue
Make an RGB LED fade nicely through the color wheel
Make a "persistence of vision" display that made an X, or the word "lewis" (not as cool as I'd hoped)
Made 3 RGB LEDs cycle through the color wheel in sequence
Controlled the cycle speed with a pot
Added a button to stop the scrolling
Added a buzzer to play a tone when the the button is pressed, "shave and a haircut" when center LED was red, and buzz if it was not (a simple game!)
Used an Ethernet Shield to ping a host, and change an LED's color based on if it got a reply or not
Send text to an LCD
Add a photresistor to the LCD, and turn on the backlight if the light level was low enough, turn it off when the light levels come up
Gyroscope with 4 LED to show tilt direction (Gyroscope sample code from http://learn.parallax.com/kickstart/27911 )
Basic Motion Detector using Passive Infrared Sensor with LED to show motion
Purchased the Parallax BOE Bot shield kit for Arduino - very cool intro to Arduino & robotics. Photo and video here.
Digital Temp & Humidity sensor with LCD display