Advertising is a key way to generate revenue on your WordPress website. Here are my top five advertising plugins for WordPress.
1) NagAds-Wordpress Plugin: (premium) Customizable modal box. Can show ads of different kind such as an image, a SWF file, a YouTube video, an iFrame and you can even embed your own code.
2) AdRotate: (free) Add and manage the ads from the dashboard and show a random banner, or multiple on site. Supports unlimited groups for banners allowing to tie certain banners to different areas of the website. Super easy management of ads.
3) WP PRO Advertising System-: (premium) Powerful features to put advertisements on your website, manage advertisers, campaigns, banners and impressions all in just a few seconds. Manage banners, advertisers, campaigns, and adzones easily.
4) WP125: (free) Manage your ads more efficiently, leaving you with more time to write new posts. Choose from 1-2 ad column display and show as many ads as you want in manual or random order.
5) AdFly Rotater for WordPress: (premium) Timed interstitial ads and banner ads. Works in every browser and control everything from page delay, max ad cap per day, and ad frequency.