Chitika

Chitika (http://www.realcontext.com/index.php?option=RealContext:+Contextual+Targeting+Engine)
RealContext uses Artificial intelligence to retrieve the most relevant ads for your page. And there's an extra feature which makes RealContext unique as well. Keywords are selected based upon which previous selections payed off and which didn't. That means there's a constant feedback process that ensures you gain better revenue from your ads. It also supports blocking certain adds and child-safe filtering and many more options.