The In-Post Ads plugin allows you to save your most used ad codes, and insert them as a shortcode in your pages or posts.
You may already use a plugin to display your ads in a widgetized area of your page such as the left or right sidebars, or in the header or footer of your page. While this does get the ads on the page, your site visitors are not likely to click on them.
This plugin creates shortcodes, which you can use inside the body of any page or post to display an advertisement. This is where your reader’s eyes are looking anyway, and it will increase the odds that they will click on the ad.