I have found that the big Leaderboard 728x90 is an effective spot to direct attention to adsense content. I have a relatively new page where I'm using a technique of a combined Skyscraper 120x600 and Leaderboard 728x90 where the Leaderboard has black links and the Skyscraper has the traditional blue. So far data shows that the Leaderboard gets about 90% of the attention. Here's my site for reference: http://computerquickfixonline.com/ Let me know what you think and please share on other effective ways to have the Leaderboard stand out from your experience.
First of all, blue links are the worst you can use. Second, if you dropped that 728 ad lower on the page it would get less clicks then the sidebar. Its on top now so people see it first. Goodluck with your site.