eliesalame @ instructables.com has written an introduction course to programming Arduino. It is focused on those who just starting now in the Arduino world.
It is meant to be a beginners guide that includes detailed explanation about the basic statements and functions. Most of the sketches I use are taken from the Arduino IDE for their simplicity. I wrote this guide when I first started working with Arduino as a way to help me code easier.
Arduino 101 Fundamentals – [Link]