We displayed ads on one of our clients website using 'Revive Ad Server'.
It is a free, open source ad serving system that enables publishers, ad networks and advertisers to:
Serve ads on websites,in video players and in apps and collect detailed statistics about impressions, clicks and conversions.
Also Define rules for delivery of campaigns and ads, including frequency capping, URL targeting, geo-targeting.
Please check on vidyutbazar.com