TopBucks, ConversionCash, AdultFriendFinder, EraserCash, CyberErotica.
As far as big sponsors playing themselves out - I don't buy it. CyberErotica.com has been around since '96 (longer?) and was recently ranked #1 by the Statistician. It was the only adult pay site I knew by name before I started in the business.
All the big boys update their tours every so often to make them look fresh.
CyberErotica is not for the weak of heart - as they only pay $50 if the person converts - nothing hurt more than when I was starting out to see those sales - and then credits, but you can do well with them promoting it as a free trial. I do well on their free email programs as well. They also have a program that pays $40 for paid trials.
TopBucks is always coming out with new sites. The new sites do appear to do better at first, but even iTeens (which I am guessing is their most popular over time) still does very, very well. Under 1:100 overall for me.
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TopBucks.com - Converting at better than 1:130
David Lace Content - Highest Quality Teen Content
ConversionCash.com - Make Money off your WebTV Traffic