The reed relay coil really should have a diode. He's getting away with it because (a) the reed relay coil can only store a very small amount of energy so when turning it off the voltage doesn't get too high to be of concern, or more likely (b) the built-in ESD diodes of the microcontroller are serving the same function, diverting the coil current to the +5V node on the Arduino.
The red LED really should have a resistor, unless it's a special +5V LED that is designed to be run right off 5V. It's one of those things you can get away with, for a while, until something starts smelling funny and giving off smoke. Then you're not getting away with it anymore.
The Gadget Shield
: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons