Adsense Deluxe is the most used plugin to integrate Adsense or Yahoo Publisher Network ads in a wordpress blog. The main reason for the popularity of this plugin is its simplicity. It installs like all other plugins (By putting the plugin in the plugins directory and activating it from the control panel). Though its named after Google Adsense, but you can also insert any other kind of javascripts in your post like Ads from YPN (Yahoo Publisher Network), AdBrite, Widgetbucks, Affiliate Codes etc. Theres no limitation of the number of the ads you can add to your control panel. You can also align the ad’s position by wrapping the adcode by a inline CSS stylecode . Its all explained here.
According to the author of this plugin, its influenced by the Adsense Wordpress Plugin by Phil Hord.

Features:
* Use simple HTML comments for embedding AdSense or Yahoo! Publisher Network ads in a WordPress post
* Choose from any number of ad styles and format on a post-by-post basis
* Globally change ad styles
* Selectively disable display of individual ad styles or all ads
* Integrated AdSense Preview tool (a sandbox) for seeing what ads will appear on a given page. (Stand-alone AdSense SandBox Tool also available)
* All settings configured through WordPress Options interface (no knowledge of plugins or PHP required)
* Easily test different ad formats and color styles across (all, or) a range of blog posts.
* (Optionally) Apply CSS formatting to the AdSense code.
* Does not display live ads when editing a page, instead placeholders are shown.
* Ads are EXCLUDED from RSS feeds — even if you have full-text feeds enabled. (new in v0.3)
* Preview your ad blocks from the AdSense-Deluxe options page (in case you forget what the ad style looks like), and ads can be clicked without penalty since they use a test account.
* Support for wp-tiger-admin plugin’s CSS in post/page editor QuickTags

Dowload The Plugin Here.

Don’t forget to donate the author or enable author reward if you use and like the plugin.