Arduino offers a wide range of Atmel-powered boards suited for various projects, highlighted on Arduino Day. The Arduino Uno, a popular choice, is based on the ATmega328 MCU and features 14 digital I/O pins, while the Arduino Leonardo utilizes the ATmega32U4 for built-in USB communication. The Arduino Due, the first with a 32-bit ARM core, boasts 54 digital I/O pins and runs at 3.3V. The Arduino Yún combines an ATmega32U4 with an Atheros AR9331 for Linux-based networking capabilities, and the Arduino Micro, developed with Adafruit, is suited for breadboard use. The Arduino Mega (2560) supports extensive connections with 54 digital I/O pins, while the Mini, Nano, and Pro Mini offer compact alternatives for space-constrained projects. The Arduino Fio is designed for wireless applications, and the Arduino Zero, a joint effort by Atmel and Arduino, provides a 32-bit extension with advanced debugging features. Additionally, the Arduino AtHeart program allows products with Arduino-supported processors to showcase their connection to the platform, with examples like the littleBits Arduino Module enhancing its versatility.