Control LEDs with Raspberry Pi

Using an old hard drive cable, I built a GPIO breakout cable then proceed to make an LED blink... a classic 'Hello World' of electronics.  I followed this diagram for the connections.

image from Embedded Linux Wiki

Plug the wires and follow these steps:

1. Boot the Raspberry Pi
2. Login as root (embrace your dark side)
3. Getting ready to output in GPIO4:
4. $ echo "4" > /sys/class/gpio/export
   $ echo "out" > /sys/class/gpio/gpio4/direction
5. Turn GPIO4 on:
   $ echo "1" > /sys/class/gpio/gpio4/value
6. Turn GPIO4 off:
   $ echo "0" > /sys/class/gpio/gpio4/value

Tada!

I'm now using WiringPI c++ library.  Here's a good reference to get started at Limina.Log. And a good pins reference table.