LED Fading Effect using Arduino – just like your Sleeping Mac - http://www.electronicsblog.org/led-fading-effect-using-arduino/

LED Fading Effect using Arduino

const int LED = 9;
int i = 0;

void setup() 
{
  pinMode(LED, OUTPUT);
}

void loop()
{
  for (i = 0; i < 255; i++) 
    { 
      analogWrite(LED, i); delay(10); 
    } 

  for (i = 255; i > 0; i--)
    {
      analogWrite(LED, i);
      delay(10);
    }
}