A while ago I did a search for revenue sharing sites and found some big, new social networking sites. There were also a few forums that allowed you to use your Adsense code, and some article directories as well. But all in all, there really weren't that many sites to be found.
This trend seems to have taken off lately, however. In particular, there seem to be many more revenue sharing article directories. And even some standard website directories are using this model, which seems to be a completely new practice.
I suspect that before long just about every genre of membership website will employ some sort of revenue sharing structure.