Some very interesting news from Google today. If you haven't read it yet:

Google have just revealed the revenue share.

AdSense for content publishers, who make up the vast majority of our AdSense publishers, earn a 68% revenue share worldwide. This means we pay 68% of the revenue that we collect from advertisers for AdSense for content ads that appear on your sites. The remaining portion that we keep reflects Google's costs for our continued investment in AdSense including the development of new technologies, products and features that help maximize the earnings you generate from these ads.
It's been the same since the start in 2003.

We pay our AdSense for search partners a 51% revenue share, worldwide, for the search ads that appear through their implementations. As with AdSense for content, the proportion of revenue that we keep reflects our costs, including the significant expense, research and development involved in building and enhancing our core search and AdWords technologies. The AdSense for search revenue share has remained the same since 2005, when we increased it.
Over the next few months well begin showing the revenue shares for AdSense for content and AdSense for search right in the AdSense interface.