Inpired by other powersupply projects, I decided to build one myself, and ended up adding a lot of junk. See the steps on how to build one.

Step 1: Get a Powersupply

This is an old powersupply I got free from my school, and it pumps out 2-22 Amps on 5-V and 0-9 Amps on 12-V. Plus it has a automatic shut down circuit that shuts down the powersupply when short circuit is detected (it barely makes any spark when you join the positive with the negative).
You can get a powersupply easy from any computer repair shop, once you have your powersupply, it's time to put it to work.

Step 2: Safety

There are many ways that you can electricute yourselfs when doing this project, so please take the following precautions building this project, and don't get shocked and get a big blister like I did.

**NEVER EVER WORK ON YOUR POWERSUPPLY WHILE IT IS PLUGED IN**
*The capacitor inside holds enough electricity to cause an extremely painful shock, so discharge these capacitor with a power resistor with resistance over 10k ohm, just bend the resistor leads to the capacitor leads on back of the circuit board and make sure you hold the resistor with a pair of pliers because they tend to get very hot.

Step 3: Planing

Most old powersupplies have a heavily insulated line that have two wires in it, when these wires are connected, it turns on the powersupply, and is usually connected to the powerswitch of the computer. If you want to use the switch it came with, then be my guest, that is what I did, but it looks a little bad. If you want to use another switch, then cut off the existing switch and add your switch to the two wires.
For the output terminals, leave nothing but 4 strands of +5V (RED), 4 strands of +12V(YELLOW), and 6 strands of common negative wire(BLACK), if your powersupply has a 3.3V output, then you can leave out 3 strands of that too(ORANGE). Feel free to use more or less strands of wires for your output, the more you have, the better it will handle when pumping high currents.

Step 4: Putting It Together

Most powersupply has a minimal out-put current, for my PSU it is 2 Amps across the +5V. If you turn on the powersupply without any load, it might just burn out or have a wild voltage. So, I chose to buy a 10Watt 10Ohm resistor to consume that 2 Amps. I also found that it heats up so much that it started to smoke! So I decided to fancy it up, and added a big heat sink from a TV, and a cooling fan from another powersupply, even with all that cooling it still heats up to about 40 degrees C* on normal operation. I also added 4 super-bright LEDs connect parallel to the resistors and a 0-5k ohm pot to adjust the brightness. All that takes up 1 wire of 4 +5V wires that you left out, and 1 of 6 negative wires.

For the indicator LED mounted on my case, I used a 512ohm 1/4watt resistor and a green LED connected across 12 volts. that takes out 1 of 4 +12V wires you left out and 1 of 6 negative wires.

And now your left with 3 RED, 3 YELLOW, and 4 BLACK. I twisted them and used electrical type to finish it off. The terminal is solder connected to 20Amp Heavy Duty Alligator clips.

Step 5: Put It Through the Case

Plan how many hole you need to drill in the case, like the switch hole or the indicator LED hole.

Fit all your out put wires through the original hole and hot glue it shut so you won't be able to pull it out of the circuit board.

And Walla, your done! Make sure it is properly grounded, plug it in and turn it on.

Please post and questions or suggestions. I will be around for the next 2 weeks.