If you are using advertisement on your WordPress blog and your advertisement is not performing well,then you should place the ads in proper place around your blog.I have found some usefull plugin which help you to generate more revenue from your blog.
The adsense attachment page  plugin show attachments with thumbnail image, and  it will show image in full size.
Now you can use adsense under the first image in your post. If there are no images no advertisement will display,Also the ads will only appear in single post pages.
This plugin  allows you to insert AdSense ads without modifying the blog template.  you can set it up to show different AdSense ads for different articles older then prespecified days means nuber of days
Use this plugin to quickly and easily insert Google AdSense to your posts, pages and sidebar by using a trigger text or calling the PHP function.
Easy AdSense is a simple plugin which prove you the option of setting the code according to adsense policy and type of ads. With its full set of features its works with google adsense
This plugin was developed to insert and manage your AdSense ads, based on the google policy
Is the simplest possible way to generate revenue from your blog using Google AdSense.  it puts your AdSense code in up to three spots in your posts and pages.
AdSense Immediately is a simple plugin to ad AdSense ads into the body of your content. It can add one, two or three AdSense block to your post

These are the few plugin for using adsense in your wordpress blog,if there is others plugin which are useful please share in comments