Your site's content and main feature is positioned smack-bang in the middle of the page (and thus is where your visitor's eyes will be looking), so that's where you should be placing your ads. I'd get rid of the two vertical ad units and place a small unit between the logo and search field. It'll look a whole lot cleaner that way and will definitely increase your CTR. For the results page, get rid of the top ad links unit and replace it with a standard AdSense ad. All the best, Liam