Oh, and if you bring your cellphone, bring your charger. I just used the hospital's phone, one less thing to worry about losing or getting stolen, but it's up to you.
Another thing we had that was nice was a small CD player and some baby nursery music. It made the rooming-in very peaceful.
When I mentioned socks, it was because my feet get cold. But also socks with grippers if you have them are very handy in a hospital for getting up to go pee.
First of all, you will be in the hospital long enough that you'll be able to send someone home for things you've forgotten, so don't freak.
Pack like you're going to stay overnight at a motel. Toiletries, shampoo, hair dryer, socks, bra, robe (but don't bother with nightgown, they provide it). If you have helpful relatives around, send someone to the store to buy some Depends. They are much handier than the ridiculous pads the hospital provides that slip all around.
For the babies, pack their going-home clothes.
Be sure the car seats are properly installed in the car.
I found it handy to have tape, scissors, a spiral notebook and pens. This is because I was taping the cards into the notebook and writing the name of the person who gave them (and what gift they brought) into the notebook, for sending thank you notes.
Bring also a phone list, numbers of friends to call to tell them you've had the babies.