It was on a blogger's site, talking about all of the various things he had tried with ad positioning and so on.
Basically he came up with:
1) make sure you're using the context-specific functionality in Google adwords so the ads reflect the page/section,
2) put the ads left and top, and a few within the content itself (like between posts, I guess, or in the post text), because that's where people will actually use them.
He claimed to have gotten a good multiple income over his old configuration. I wish I could find the damned link, because there was quite a bit more to it.