Cash Keywords has a good reminder that Adsense has a feature that allows you to Create Rotating Adsense Ad Colours which is one technique that can help overcome ad blindness.
I think this is a particularly helpful tool for those blogs and websites with a lot of repeat readers. For example a site like Engadget (which has a very loyal readership) rotates the style and colours of its ads every impression. In doing so they change the look of their site subtly every time a reader logs in and in the process give their ads every chance of having their ads seen.
So if you’ve got loyal readership consider rotating your ads. On the flip side if your traffic comes largely from search engines it may be smarter to find the colour and design that works best and to stick to it rather than risk having lower performing configurations appear on your blog.
How do you do it? Here’s Google’s explanation: