OpenX

OpenX, formerly called Openads, is the most popular ad server solution when measured by number of publishers using it. It has 35,000 publishers using the software on 150,000 sites in 140 different countries and in 20 languages.

OpenX Hosted, contains the same software found in the original OpenX Ad Server, which allows publishers to completely control their ad space. This product allows publishers to use the software to operate all aspects of ad serving while OpenX provides all the hardware and back-end infrastructure, leaving publishers free to focus on their advertising revenues.

OpenX is an open-source advertising server that is licensed under the GNU General Public License. It features an integrated banner management interface and tracking system for gathering statistics. The product enables web site administrators to rotate banners from both in-house advertisement campaigns as well as from paid or third-party sources, such as Google's AdSense.

In Dec 08 Techcrunch reported very rapid growth for OpenX in both usage and revenues.

The company was was originally based in the UK, but has now moved its main headquarters to California with offices in London and Poland.