I think the best sources on line for adsense generally include case studies from people who have just started to earn. They keep a progressive journal of their Adsense activity and keep posting about it in some forum or some place.
One of the pdfs I recently downloaded using some torrent ( you wont get the Joel Comm book using torrents though , and it is not of much help ) .
I downloaded the “Still Alive and Well “ pdf from somewhere in the net only to find a boring case study.
Some of the interesting and the most reliable ones are from Google itself. Google is hiring people with good communication skills etc to help people get an insight into Adsense by these case studies.
Google themselves have admitted to people doing arbitrage, but then again with each person earning something indirectly means Google making money out of it, so don’t worry if you are using Adwords to find out the high paying keywords , in some way or the other Google benefits.
Here in this case study , Dr Carter ( though the name sounds phony ) uses three google tools Froogle, Adwords and Adsense to make his mark.
Good luck guys.
I will start my Adwords campaign one month from now ( June 20 , 2008 ) only to learn my way.