Ad Injection is a complex, robust and extremely in-depth plugin that allows you to place advertisements on your WordPress site. You can place ads just at the top, throughout the body at random and at the bottom of your page.

It supports a lot of customization. You can choose to only have ads at random, or only ads at the top, or only ads on the bottom or any combination. You can choose only to show ads on posts that are older than a certain amount of days. You can choose to only show ads to people who come from certain traffic sources, or exclude ads from those traffic sources.

You can learn skills from this book how to install, customize and use Ad Injection.