The hospital should give you mesh underwear after you deliver, into which they stick huge pads. I took a bunch of those (underwear + pads) and wore them for weeks after giving birth (sexy, I know), or I just put the pads in my normal underwear. I never bought maternity underwear either.
Anyway, here’s what I brought to the hospital that I used:
toothbrush, toothpaste, shampoo, face wash
lansinoh/nipple cream for nursing
my maternity leave forms for work
car seat (actually my husband brought this later)
phone (for taking pictures)
here’s what I brought but did not use:
outfit for baby (she just wore the hospital outfit that they gave her)
I did not bring a change of clothes for myself. I know that’s weird, but I am a very light packer. 🙂 As soon as you’re admitted, you change into a hospital gown, and then you stay in that for the duration of your stay, so my clothes were pretty clean. And, as everyone says… your tummy is still pretty big when you leave, so having maternity pants was nice.
ETA: Reading other people’s comments made me realize — of course not everyone stays in the hospital gown for their entire hospital stay. I just did because a) I am lazy, b) I was bleeding like crazy and didn’t want to mess up my own clothes, c) the loose, light gown was actually very comfortable, and d) I just had a baby! I’ll wear whatever I feel like, damn it! 🙂