<a href="https://www.atmel.com/products/avr/default.asp">  General page about avr products </a> <br>
<a href="https://winavr.sourceforge.net/"> free c compiler for avr </a> <br>
<a href="https://www.avrfreaks.net/"> forum for avr people, also has lot of projects </a> <br>
