"Well known/good networks"??? TextLinkAds, TrafficSwarm, CasaleMedia, Advertising, FastClick, BurstMedia, TribalFusion, Azoogle, GlobalInteractive, AdBrite, Adengage, RealMedia, Kontera, Avnads, ValueClick, RealTechNetwork, Reduxmedia, and, Dotomi, Clicksor.
I haven't used any of them. I do my own advertising. Meaning, I contact the webmasters on my own. I got that from my fellow advertisers who, like me, are much older and experienced than many of the webmasters out there. They do heavy advertising. They seem to like these networks. You just have to choose one, or more than one, that YOU like the best, and, that fits within your budget.