Favorite set-up and/or testing CD?

What are some good set-up and testing cd's for two channel audio systems? Or, are they even worth using? I have no experience with them, I just came across one produced by Stereophile (I think it was them) and it sparked my curiosity. If you have one (or more) that you like, what are they most useful for? Thanks, Jb3
Stereophile, RCA, and others have made these CDs to test the basic setup. Ultimately, you need to set up by listening--your ears.