"The Adafruit Feather are a complete line of development boards from Adafruit that are both standalone and stackable.
They're able to be powered by lipo batteries for on-the-go use or by their micro-USB plugs for stationary projects.
Feathers are flexible, portable, and as light as their namesake.
ATmega32u4 @ 8 MHz with 3.3 V logic / power 3.3 V regulator with 500 mA peak current output USB native support, comes with USB bootloader and serial port debugging 20x GPIO Hardware Serial, hardware I2C, hardware SPI support 8x PWM pins 10x analog inputs Built in 100mA lipoly charger with charging status indicator LED red LED for general purpose, blinking 4 mounting holes Reset button 51.2 x 22.8 x 8 mmBuilt-in nRF51822 Bluetooth Low Energy module"