I find it interesting almost all of the big content sites have AdSense/Overture/Kanoodle/AdBrite links on them. Wouldn't it be more profitable to sell direct advertising to major advertisers? If I were running sites like these, I'd prefer to have a few big clients paying major money for a campaign rather than trying to make money off of text links, because I could cultivate a long-term business relationship with these advertisers. It seems to me this is how to grow advertising revenue for a content company (other than, of course, publishing good content). But, since all the big sites devote significant space to text ads, it looks like I'm wrong about this?

I would love to know how much CNN makes off of its graphical ad campaigns vs the Overture links it has embedded in the articles.

I don't have any experience doing this, but from what i've heard it is. You should be ready by learning how to use a proper ad management tool. Such as phpadnews or hosted ad servers.