Depends where you live and hospital provides diaper.. but I always brought clothes for home a pillow slippers lip chap some munchies diapers wipes a book laptop or mini DVD player some movies clothes for baby blankets car seat hat for baby pacifier if your using one. An extra bag for pamphlets papers etc tooth brush tooth paste shampoo conditioner towels cause hospital towels are ridiculously small and some bigger comfy underwear and pads extra absorbent incase hospital doesn't provide.. a little makeup to liven your face up when you leave if you want. Elastics for your hair..and last but not least a water bottle with a squirt top if you have a vaginal birth that bottle filled with warm water to pour on your self when you per will do wonders cause it burns when you pee. And stool softners.. that's what I brought it's a lot but it's what I needed.
Comfy going home clothes for you, missing bra if you're nursing or just a really comfy bra, toothbrush, hairbrush, contact stuff etc that you would take on a normal overnight thing, makeup if you want it for after birth pics, pads for after birth bleeding, flip flops or slippers to wear if you're going to walk during labor, camera, baby clothes, a baby blanket, diapers (they might give you some at the hospital...), your baby book if you want to get their footprints in it. Mostly importantly - CARSEAT! You can't leave without it. Those are what I can think of I'm sure there are tons of awesome printable lists if you Google too.