#include <stdlib.h> // C standard library
#include <stdint.h> // (C99) Standard Integer Types
#include <avr/io.h> // Register address definitions
#include <avr/interrupt.h> // I use interrupts in almost every project, so include the interrupt vector definitions etc.
#include <util/delay.h> // Delay functions.. I always use those. At least when debugging.
#include "atmel_avr.h" // This is my own file that contains useful general purpose macros like bit-manipulation etc.