Conversant (formerly ValueClick Media) currently represent the pick of the independent online ad networks due to their great support and service, as well as decent payouts ($0.50+ eCPM for banners/skyscrapers and $3.00+ eCPM for pop-unders). They always answer any questions promptly and politely, and most importantly pay on time every time, on the 20th of the month following you earning the revenue (NET 20).
They offer one of the widest options of advertisement types of any network, ranging from traditional banners and skyscrapers to the larger modern standards, pop-unders. Most interestingly, they have recently introduced an interstitial, which is a full page ad displayed for 10 seconds when a linked is clicked before forwarding the user onto the next page. This is a very useful addition for sites with long, multipage articles, as they are finally able to monetize the article as a whole in a similar way to magazines showing ads between pages.
The interface has had a major overhaul in recent years and now offers one of the easiest and most advanced of any network available, giving publishers some great graphically represented real-time statistics, and lets you (de)select each campaign individually and by content filter. The eCPM is shown for each campaign, as well as a number of other things, although this lets you compare all campaigns (CPC and CPM) on how well they are performing for you personally. This means that you can deselect the worst performing campaigns and make use of Conversant’s industry leading defaults manager, so you can send your remaining traffic to any number of other ad networks. They have even recently released floating defaults which allow you to set up default campaigns which are put into rotation at a set eCPM, so working as a real campaign.
Overall, Conversant is a great company to work with, and is a very reliable source of income, constantly improving and adapting to improve their services.