Popunders are a great way to monetize low to medium quality traffic. For example if you run a freebies, wallpaper, or viral content site, you may have a ton of traffic. But that traffic just won't earn you anything with traditional ad networks. Yet it will cost you in bandwidth and server costs.
I run a number of these sites and I use popunders to monetize them. The visitors don't mind either. Especially with a freebies site – they are getting something in return, and are happy to be shown an ad. Unlike popup ads, popunders are shown below the content. This way the user isn't taken away from your website.
So what is the best popunder network? I've tried out a few but…
The Best Popunder Network
By favorite popunder network is popcash. I like the fact they only show one ad to a user per session. This means a user can browse around one of my sites and will only ever be shown the one ad.
Popcash offers fast withdrawals payable straight to your PayPal account. Recently they have started charging a $1 withdrawal fee which bugged me a little. But I do earn thousands from popcash so It doesn't really impact earnings overall.