Food. Lots and lots of food. I was starving after my son was born, and I didn't want to put him down long enough to cook. So easy to fix stuff (for you to fix or to get someone else to do it for you)
A big water bottle. I was also dying of thirst. The hospital gave me a big 32 ounce mug, and I probably drank 10-15 a day the first week.
Nursing bras. For the early days of engorgement, I used the $8 ones Walmart sells. Plus, the sizing isn't really exact (I sent dh with the instructions "buy the biggest size they have"--he came home with 3 different sizes, and they all worked fine
Nursing pads. I bought the cloth ones before the baby was born, but I needed disposable for several months. I like the Lansinoh brand.
Second on the granny panties
Overnight maxi pads. I was honestly glad to get home and use the thin (still overnight, but thin) kind from the grocery store, instead of the huge thick diaper ones the hospital had.
Lots of jammies. I have an embarrassing number of pajama pants, and I wore them for a week. If there was blood or spit up or what-have-you, it was no problem to change without thought of laundry. I wore pajamas for a week to remind myself to take it easy, that I was recovering, and that I shouldn't be expected to be right back to normal. YMMV.
At least 2 sets of sheets for your bed. I leaked like a faucet once my milk came in. Also night-sweats because of the hormones. And the blood. It was nice to rip off dirty sheets, put a clean one down, and go right back to sleep. I'd do the laundry in the morning.
Ibuprofen. I had a c-section, and this was my friend.
Something to watch on TV or magazines to read or movies to watch. We have TIVO, and during the last weeks of pregnancy, we taped all 10 seasons of The Waltons (yes, bizarre, I know). I'd nurse and watch the Waltons, nurse and watch the Waltons. It took several weeks before I could nurse and get at the computer, even more weeks before I could nurse and read a book/magazine, so TIVo and Netflix were our friends those first few weeks. I've had friends that get hooked on Law and Order reruns while nursing newborns. LOL