While talking with one of my web design clients, the question of where to put certain design elements came up.
I made this numbered image so that we could talk about regions of the Google heatmap image while working on his new site. The cool feature of this heat map is that it is based on the big G's extensive Adsense data to recommend placement of ads for the most clicks (darker is higher click density).
Are you keeping these sorts of test results in mind as a starting point for your own tests on new sites?
Update (May 10, 2011): through "random" connections this evening I just ran across Michael Campbell's Ultimate Heatmap report which overlays the major advertisers' heat- and clickmaps to produce his "ultimate" map. The report also includes the main ad sizes to consider and 9 heavily tested templates for advertising on blogs. He makes the same suggestion of using his results as a starting point to run your own tests.