Microcontroller board Arduinoesc All pins on the Atmel32u4 chip have been split out into a breadboard-friendly configuration. I couldn't locate a 32u4 breakout board that gave me access to all digital and analog pins. (I'm not sure why.) I required all of the io pins for a project.
What distinguishes it? All I/O pins are accessible through breadboard-friendly headers, and it has a full-size USB connection for dependability.