Feather is a flexible and powerful family of microcontroller main-boards (Feathers) and daughter-boards (Wings) with a wide range of capabilities. They can be plugged into a breadboard for quick prototyping, have built-in battery connectors for your on-the-go projects, and most have built-in lipoly chargers!
Once you pick your Feather (the brain of the system), you can (in theory) add as many Wings as you would like. You can either stack them, or quickly prototype using a Doubler, Tripler, or Quad FeatherWing. Most Feathers and FeatherWings have example code and libraries written in Arduino C/C++ and CircuitPython.
With over 100 Feathers and FeatherWings, the opportunities are endless.