Arduino Pro Micro Atmega32u4 5v 16Mhz Development board

The Pro Micro is similar to the Pro mini except with a ATmega32U4 on board. The USB transceiver inside the 32U4 allows us to add USB connectivity on board and do away with bulky external USB interface.
2. This tiny little board does all of the neat-o FOR Arduino tricks that you’re familiar with: 4 channels of 10-bit ADC, 5 PWM pins, 12 DIOs as well as hardware serial connections Rx and Tx. Running at 16MHz and 5V, this board will remind you a lot of your other favorite FOR Arduino-compatible boards but this little guy can go just about anywhere. If you’re supplying unregulated power to the board, be sure to connect to the “RAW” pin on not VCC.

Features:
ATmega32U4 running at 5V/16MHz
Supported FOR Arduino IDE v1.0.1
On-Board Micro-USB connector for programming
4 x 10-bit ADC pins, 12 x Digital I/Os
Rx and Tx Hardware Serial Connections