Webmaster Articles has a good post about increasing your CTR (click through rate) on Adsense. They write some good posts – similar to some of what I’ve written in my Adsense for Bloggers Tips. Here is one that they write that I’ve found to work very well for me also.
“#2 Blend the background and border to match the page’s background. You don’t want to trick visitors into clicking, but you don’t want them deadened by banner blindness either.”
Read more at Google Adsense: Tips to Increase CTR