I've created a simple tool to calculate Adsense earnings in relation to impressions and clicks. It's mainly designed to see how well each channel performs per page view but it also seems to work reasonably well for date reports (up to 31 days at a time).
I initially made it for myself but I figure I might as well share it:
http://www.mediacollege.com/internet/affiliate/adsense
Would appreciate any comments or bug reports.