ARDUINO Leonardo like board with ATMEGA32U4.
Breadboard friendly design.
ATMEGA32U4 microcontroller, all in one USB communication no need for external FTDI chip.
Input power supply taken from mini USB
feeds power to the breadboard bus
work both on 3.3V
UEXT connector which allow many existing modules like RF, ZIGBEE, GSM, GPS to be connected
he LEDs and the BUTTONs are on the edge of the board so there is easy access even if the boards have shields on them
mini USB connector is used which is common and used in most cell phones, so you do not have to buy other cables