Back and the stiff arm pull down
I happen to like this exercise great for lats
Start Position: Stand and face the weight stack of a cable crossover machine. Grasp the bar with a slightly wider than shoulder width grip. Keep knees bent, lean over just slightly, and moderately arch your back. Your arms should be nearly straight, but elbows should not be locked. As always, abs tight.
MidPoint: Keeping arms straight, bring the bar down in an arc until it nearly touches your upper thighs. You should really feel it in your lats.
Finish Position: Reverse the arc and slowly return to the starting position until you feel a good stretch. 10-12 reps for each set.
http://www.fitnesslynn.com/back5.htm
that site has a great picture of how to do this exercise
i tend to keep my hands more on the straight part of the bar