Everyone here has a different opinion.
But mine is google adsense is one of the best.
It does take a little front end work to setup. But it works quite well, Once you go through the hurdles.
Other than that there is a new forum here for this type of discussion;
https://www.ubbcentral.com/forums/ubbthreads.php/forums/55/1/Website_Monetization.html
