Curious which would be the best on a casual site. I do not know much about MSN adCenter, so I wont ask about that. But as for the other two which pays the highest? thanks
I've heard that yahoo and google are both pretty good. Some people can make just about as much with yahoo as they do google. Both incorporate relevancy of ads to match the content of the site.
If you want to try something new and unique, checkout my site TextAdMarket (in sig). You setup your ad and choose a "price per day". Assuming advertisers want to advertise on your site, you will get the same flat amount each day, rather than fighting for clicks, impressions, or actions.