Best Pay-per-click Engine : Google Adsense
The Most popular money making mechanism on the web is google Adsense. Web Publishers  have earned thousands of dollars on to their pockets even with small amounts of traffic. Before Google Adsense was introduced, Only high traffice websites are benefited from advertising. To Qualify to  Google Adsense even there is no limitation on the traffic for your website .Even with single hit a month one can run a google Adsense account.
Google Adsense is an Context sensitive Pay-Per-Click Program.The ads displayed by google are in-line with the topic of your website. And also the ads can be in textual format which can be completely blended with your text. Google display the ads on your site based on keywords.The main reason behind earning more money with google adsense is competitive bidding in between the advertisers on Various Keywords.
 Keep watching this space for more on google Adsense