Well, some of the God Members have a lot more history with the ATMega than some of the more recent God Members (me especially, I've only been Arduinoing since August.) But there are some Electrical Engineers here, some Software Engineers, that always helps 
If you browse the ATMega 168/328 datasheet, there is a table there that lists all the instructions if you really want to do some low level programming.
I did some assembly level programming in college, some higher level programming since then, but mostly hardware design over the years. I am finding writing in arduino-code to be pretty straightforward.
Browse the datasheet, see just what kind of non-volatile memory it has, then google that to see how transistors can be made to store bits after power is removed. It can be quite fascinating.