I’ve noticed something already. It seems that in posts with less text in them the advertising isn’t nearly as “targeted” as it is on the longer posts. Apparently adsense needs some minimum amount of text from which to draw conclusions concerning the topic being discussed. For example, this post is rather short (70 words or so), Hit the permalink and see how relevant all of the ads are.
Just copy this code and paste it on your site where you want the link to appear: