A simple board that breaks out pins from a MicroSD socket, for flexible use with a breadboard.
MicroSDs are great for use with microcontrollers because they support the SPI protocol natively. See for example the Adafruit tutorial on how to use the microSD library.
Make sure you are operating on 3.3V! It works fine with an Arduino Micro, but for an Arduino Uno you will need a level shifter.