I also think the Atmega cheat sheet is outstanding.
A few years ago I discovered that my programming skills could be used to make real-world things move and flash and beep - I haven't looked back since! I love sharing what I've learned along this pretty bumpy (but very exciting) journey into the world of embedded systems - and that's why this website exists. In addition to the website, I write a series for Nuts & Volts magazine that helps readers to move beyond the Arduino and into the world of AVR. I'm a dad with a couple of energetic youngsters and a really cool wife!