how to make an led turn on when something gets close to an ultrasonic sensor Hey I just started using arduino and so far can't get any help with how to write a code for an led to turn on when someone gets in range of a three pin ultrasonic sensor, and off when they are out of a specific range.

Any help?
Try with this and check that at least you can reproduce the desired effect:
http://www.arduino.cc/en/Tutorial/Ping?from=Tutorial.UltrasoundSensor

Then you can refer to this for the part related to driving the LED:
http://www.arduino.cc/en/Tutorial/Blink?from=Tutorial.BlinkingLED

Since the ultra sound demo already calculates the distance, you can do the test on that to decide when to turn ON/OFF the LED.