I know that this has been said, but lets say it again.
Deadlifts. You can do just about every other back excercise in the world, and it might build your back. Deadlifts build just about every part of the pullling chain, even if not equally. Deadlifts build up raw power, they make you strong. It teaches your muscles to work together,and it helps to correct postural imbalances. If there is one excercise thatyou have time to do, make it this one.
I used to do pronated barbell rows and weighted chin-ups. I put my routine on here, and someone said I needed more pulling movements. I added wide grip pull ups and underhand barbell rows, should width. Let me tell you, those wide grip pull ups really really really jack my back, I can feel each individual part being used in the pull. I like the underhand barbell rows because I feel a lot of burn in my biceps, so it is like getting a two for one excercise.
The people at work tell me that I have no neck, but I do not train traps. However, if find that most back excercises, especially deadlifts, train the traps. Another great way to train the traps is behind the neck presses, military press and bradford presses.