Get the narrow grip bar that is used for seated rows and hook it over the chinning bar and do chins...
Cleans are an AWESOME but overlooked back builder. I use a modified version where I stop the weight at my mid quad height and not all the way to the floor. (or you can do them sitting on a bench with dumbells.
Another exercise that will really get the back to cramping and contracting (which you want) but will get you puzzled looks is Low PUlldowns to the Front. Take a seat at the lat machine just like you normally do and use a weight that is about 50-60 pounds lighter than what you would normally choose.... medium width grip (inside of thumbs out further than shoulders) and remain seating perfectly upright (no leaning)... pull the bar all the way down until it touches your upper ab. Yes, upper ab. In order to do this, as soon as the bar travels down and past your throat, you will subconsciously have to angle your wrists down and your elbows back in order to get the bar to make contact with your upper ab area. Do about 10 - 15 reps. This is an exercise where you WANT to get the contraction going on over and over again.
Also, practice contracting your back. We can all contract our chests without moving our arms (bouncing the pecs) and we can all bounce our calf muscle up and down without flexing our foot... but it is shocking the number of people who can't contract their backs without moving their arms when they are hanging limp by their sides. Master the contraction every chance you get.
