Arduino Uno Schematic Diagram: A Comprehensive Guide
Arduino Board Template - Uno R3 Full Size | Projects | CircuitMaker
General purpose board using Arduino MEGA PCB template, with Arduino Nano controller board, LCD+Keyboard, DS3231 RTC, NRF24L01 radio, and DS18b20 temperature sensor - Share Project - PCBWay
Nice drawings of the Arduino UNO and Mega 2560 | Arduino Blog | Arduino, Embarcados
shield layout for DUE/Mega - Arduino Due - Arduino Forum