Thanks Kiril!

Here's the article you are talking about:
http://news.jeelabs.org/2009/05/14/power-consumption-baseline/

I hadn't noticed that there is a prescaler for the main system clock on the Atmega8 series. Just looked it up in the datasheet now, really interesting. And the jeelabs.org site has some cool projects :).

Another obvious thing do to to lower power would be to turn off all the unused internal peripherals.