I've read on a few websites (BodyBuilding and t-nation) that Box Squats are good exercises to help with dead lifts. You don't get the full range of motion and through doing them I seem to feel more tension on the back rather the glutes or legs...so, are they somehow more like dead lifts? Is it the drive from the box that provides the benefit to dead lifting?
Mark Rippetoe is adamant that the deadlift is not a squat with the bar in your hands. That said, I've used box squats for checking my squat pattern. I find a bench, stool, or box such that when my butt hits it, I've just broken below parallel. I just tap the box and come up. There are versions where you pause for a second before rising. The idea is to be able to keep your eyes looking at the right spot on wall and not try to look down to check your depth. The main point, of course, is to not fool yourself that you can do real squats. Now I check how low I can go (with no weight) before my back starts to round and try to find a box that will help me stay safe. Squats and deadlifts will improve your ROM but it's important to only use the ROM you have. Don't almost squat so you can show off, don't squat deep if your pattern breaks (butt tucks in and back rounds). The same applies to the dl - use only the ROM you have - you'll get more as you get stronger.
I've never done them, but I hear that sitting on the box allows (produces? demands?) a greater hip drive than a boxless squat. My current understanding is that hip-drive-powered squats have more overlap with the deadlift (specifically in the posterior chain) than, say, a front squat or a high-bar back squat.
But again, I've never box squatted, and have never used squats to help my deadlift. Squats are for squats in my programming. So, your mileage may vary.