OpenX offers webmasters and web owners solutions to monetarize their website. They have developed a very powerful open source script to setup your very own ad server. It allows you to operate and manage your advertisement campaigns through their easy to use and innovative interface. It provides you with all the necessary tools to maximize the performance of your ads. They also offer OpenX Hosted, where they provide the hosting and hardware, leaving you to concentrate on just the management portion. This allows the user to make full use of their software, without worrying on the hardware. Furthermore, they have a very active community. Please check out their forums for more.