I was given two A4 printed sheets of things they suggested I took into hospital with me. Ridiculous. Mostly I divided it into: things to wear/use in labour, things to wear/use after labour, things for the baby.
So, in labour included things like a nightgown, a soft bra/bikini top (hoping for a water birth!), phone charger, etc.
For baby: many clothes (layers), a blanket, lots of nappies, a hat. I've put the first outfit and nappy into a food bag so DH can just grab it easily when DD makes her appearance, rather than having to rummage about.
After labour was: towels/wash bag, clean nightgown, big black knickers, breast & maternity pads, outfit to wear home, book for the ward, etc.
If you end up having to stay in then your DP can always go home and grab longer-stay supplies.