Sometimes when I need to slow down really quick for a corner, I pop the car in neutrel and press the brakes. My thinking is that without the tranny driving the wheels, the car will slow faster with less stress on the tranny and brakes. After the corner I put it back in o/d and take off. Am I really hurting things more when I do this, or is it just one of those stupid things that doesn't really matter?

The transmission will actually help slow you down, so what you're doing is wearing your brakes out sooner. This is more of an issue with a manual transmission, where you can manually downshift to save the brakes, but you're really not HELPING your trans, and you ARE wearing out your brakes sooner.

i was thinking more of him wearing out the trans and motor mounts. i might be wrong though.......

The only time I shift to slow down is when I'm sliding on ice and there is traffic in front of me.

I will downshift to first and apply the brakes. It seems to help me stop better. I only use it in emergency cases because it is not good for the car.

Best thing to do in NORMAL situations, is just let the foot off the loud pedal, and put it on the screech pedal.

IMO, you're putting MORE stress on the tranny and brakes with your method. Especially with today'* computer controlled cars.
Use The Brakes, when you want to slow down. And Don't(i.e. Never) take the car out of gear! It'* A Lot cheaper to replace the pads on the brakes than to diagnose/repair a problem with the transmission.

I would only do it in exteme cases.

I was stuck on black ice a couple times and had to do it.

keep your distance from other cars, get the big picture meaning watch for stale green lights. If the light has been green for a while you might wanna slow down because the light is going to change. Then you wont have to worry about braking hard.

Both of these strategies above would be better on a rear-wheel drive car than a front-wheel drive, because in the Bonneville these strategies are only acting on your front wheels. With your front wheels dragging down the car but your rear wheels not (if you're not on the brakes), in a slippery situation you have a good chance of suddenly swapping ends or spinning out.

In a rear-wheel drive car you're throwing out the anchor on the back end of the car instead of the front, which will help keep the nose pointed in the right direction.

The transmission isn't "pushing" the wheels when you get off the gas. The engine isn't being pushed anymore, but because of an automatic'* nature, it has a much more gradual slow down over a manual. When you get off of a manual, and the clutch is fully engaged, you know it.

Conversely using the Transmission on steep down grades will help save your brakes from early death.