http://arduino.cc/forum/index.php/topic,43903.0.html#10

gistfile1.txt

int pin = 13;

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

void loop()
{
  // SOS
  dot(); dot(); dot(); 
  dash(); dash(); dash();
  dot(); dot(); dot(); 
  delay(3000);
}

void dot()
{
  digitalWrite(pin, HIGH);
  delay(500);
  digitalWrite(pin, LOW);
  delay(100);
}

void dash()
{
  digitalWrite(pin, HIGH);
  delay(1000);
  digitalWrite(pin, LOW);
  delay(100);
}