What are some alternatives?
AdHitz - Lets you sell ad space on your site. You choose the details and then paste the code to your site.
OpenX - Ad technology platform available as a hosted service or as an open source download.
PropellerAds - Propeller Ads is a full and self-service advertising network providing comprehensive and industry...
AdRoll - AdRoll is a leader in retargeting display advertising. Draw the right people with the right strategies.
AccountJoy - Execute effective advertising campaigns to exactly the accounts you want to target.
Epom Ad Server - An ad serving solution for publishers, advertisers, ad and affiliate networks