This project is not necessarily original and has been done by many people.
The most "together" project is that of this guy: http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply
There are a multitude of other projects, but I feel mine and his are the best I've seen so far.
Issue of the Resistor
Power supplies need a certain minimum load to work properly. The min. load for mine is around 0.8 amps. Thus if you plan on powering LED's or other such low-power device exclusively, you'll need a resistor to provide a load. Otherwise you will damage the PSU.
A meaty 10-Ohm, 10 watt resistor from Radio Shack is a good choice. Wire it across 12 volt and ground.
-12V and -5V lines
It has been brought to my attention that the -12V and -5 lines are pretty handy for diversifying the voltages this thing can produce. These are the white and blue wires I told you to cut earlier.
Of course, adding them is simple, it's just a matter of getting two extra binding posts and connecting the wires to them. It's just a question of "Do I need these?"
I didn't, all I really needed was the 12V line. But as I said, if you need them, they're easy to install.
Still going strong! This little PSU has been super handy.