I started using this drill to teach my athletes to engage their lats more for deadlifts and Olympic lifts, but I quickly discovered that it can turn the deadlift into an even more complete back-builder.
Sweeping Deadlift
A regular deadlift works great for the lower and mid-back as well as the traps. There's some lat involvement to keep the bar close, but not enough to stimulate maximum growth.
By using a resistance band attached to the bar and a post in front of you, you drastically increase the force the lats must produce. The sweeping deadlift will help you build strength in all the muscles of your back. It's such a good overall strength-builder that it will even help you with pull-ups.
Perform sets of 5 reps, 4-6 sets. Use a bar weight that's about 70% of your maximum deadlift and walk back far enough to feel a good tension in the lats.
An even better movement for the upper back and lats is the same exercise but using the wider snatch grip. Alternate both. When using the snatch-grip version, use about 15-20% less weight.