I found this tutorial on
http://moodle.robotics101.com/index.php. It's very good for begginers who don't know much about programming. Although it is for a pic, a lot of the concepts are the same as avr. Normally you have to make an account to get them, and although it's free it's annoying so I got the pdfs for you. They're attached at the bottom of the page. Also at times the author makes references to later chapters which he hasn't put out yet or plans to put out considering he hasn't touched the site in forever. If you don't understand the electronics I have a similair post on the electronics page.
http://www.societyofrobots.com/robotforum/index.php?topic=6764.0
