Feather 32u4 Basic Proto has a free prototyping space on the board. Feather is a new development board series from Adafruit. As the name suggests, Feather boards are thin and light. Feather is designed to be a new standard for open source development platforms.
Feather 32u4 is based on Atmel’s ATmega32u4 clocked at 8 MHz and at 3.3V logic. Atmega32u4 has 2K of RAM and 32K of flash, with built in USB. Therefore this chip not only has a USB-to-Serial program & debug capability readily (and there is no need for an FTDI-like chip), but also is able to act like a mouse, keyboard, USB MIDI device, etc. Arduino IDE supports this chip pretty well, so it can run almost all sensor/library.
For easy use in portable projects, Adafruit added a connector suitable for their 3,7V Lithium polymer batteries and built in battery charging. There is no need for a battery, the board can be powered directly from the micro USB connector. If you want to use it with a battery, you are also free to run your project with a battery and then plug in the USB for the battery to be recharged. Feather boards will automatically switch over to USB power when it is available. The battery is also tied through a divider to an analog pin, so it is possible to measure and monitor the battery voltage and detect when it needs a recharge.
Feather 32u4 Basic Proto has some extra space left over, so a tiny little prototyping area is left free on the board. If you just need to attach a button or sensor, you can use this prototyping area directly instead of wiring them from the breadboard.
The board has a USB bootloader, so you can use it with the Arduino IDE. The pack also includes some headers for you to solder them and use in your projects or on your breadboard.
Note: USB cable and Li-Po battery are not included.
Adafruit Web Page: https://www.adafruit.com/products/2771