What are some alternatives?
OpenX - Ad technology platform available as a hosted service or as an open source download.
Google AdSense - Use Google AdSense to make money online by placing ads on your website and YouTube channel. Start monetizing your website with Google AdSense today.
AerServ - AerServ offers monetization solution for mobile publishers.
ONE by AOL - Ad Serving and Supply Side Platform (SSP)
Epom Ad Server - An ad serving solution for publishers, advertisers, ad and affiliate networks
MoPub - MoPub is a mobile monetization platform that helps publishers drive more revenue from advertising and mobile transactions.