Copyediting L, a editing discussion list, is highly recommended for anyone considering doing substantive or copyediting
The list is hosted at the University of Indiana, with subscribers all over the world.
A wide variety of issues are discussed -- from pricing to grammar to differences of usage.
The list is high-volume, not for the faint of heart, and filled with seriously bright-to-brilliant people. However, if you are an editor or aspire to be one, it's the only place on the net to be.