Dave writes –
Sure power supply projects aren’t that sexy; but they are, generally speaking, the foundation for every electronics project. The voltage output for this project is 5VDC, and a practical output that can be applied to a wide variety of digital components. Even better, this power supply has a 2-pin plug that can be quickly and easily snapped into a common 2-pin header for a reliable and solid power connection. Add a pushbutton ON-OFF switch and a USB rechargeable interface and you have a versatile power supply that can be slipped inside your pocket.
HOW TO – Make a Rechargeable, pocket-sized 5V power supply – Link.