I'm working on an ATX power supply but it lacks the compact portability I need in a simple power supply.
This cost about $5.50 with the step down transformer being the most expensive part.
Old power chord (free)
Step down transformer ($3.00)
Full Wave Bridge rectifier (50V 4A) ($1.50)
5V regulator (I used an L7805CV 1.5A max) ($1.00/3)
smoothing capacitor (I used 100 uF 35V (free))
And the essentials: soldering iron flux solder, electrical tape, heatshrink tube, pliers, lighter, ect.
Step 1: Setting up the Transformer
Wrap it in electrical tape
Shrink the heat shrink tube
Plug it in and make sure it has some sort of output, actual voltage out doesn't matter.