You can easily build a barebones Arduino yourself. This project shows a breadboarded Arduino without an FTDI chip. This means no USB connectivity (this could be however accomplished using a USB-Serial breakout board).
Use an ATMEGA168, a 1kΩ resistor, a button, two 22pF Capacitor, two 10µF Capacitor, 5V Voltage Regulator, and a 16MHz clock crystal. You could program the chip with a USB-Serial breakout board or you could program the chip with an Arduino board and then pop it in the circuit. The power source should be at least 7 volts (we don't have that part yet).