I don't like regurgitating information on the Internet as I figure you would be reading those sites I'm sourcing if you were interested in that information. However, every now and then something interesting appears and I think it's obscure enough that you probably haven't seen the article and would be interested. This is one of those posts.
"oweb.co.uk have posted an article, which is actually a summary of a discussion on one of their boards":http://www.oweb.co.uk/2005/10/19/increasing-your-adsense-ctr-1/trackback/, about a method to increase the click through rate on banner ads. It's nothing ground breaking, but the claims are impressive.
*The technique is to simply stick relevant pictures next to your banner ads to draw attention to them.* The pictures also serve to dress up the ads slightly and give a more interesting and professional feeling. Check out some of the example ads on the second page of the article if your interested.