This is a clone of the Arduino Uno. You will need a USB-to-FTDI connector to use this. Power it with 5 Volts.

Etch this on a PCB, then put the components on it.

Part list: 1x Double sided cooper PCB; 3x 3 pin female headers; 1x 6 pin female header; 2x 8 pin female header; 1x 16 mhz resonator ; 1x ATmega 328p microcontroller with Arduino Uno bootloader; 1 green LED;