A new plugin called [tag]AdSense[/tag] injection seems to be a very interesting plugin for [tag]Wordpress[/tag]. This plugin will place your AdSense ads into different positions on your blog. When a visitor visits several posts or pages, your AdSense ads will be in different positions. This way, if your visitor didn´t see them on the first post, the chances might be that he or she might see them better in a different position on the site.
I found the information about the plugin at Problogger, you can get even more information about the plugin at this site.