Quiche is one of my favorite things to make postpartum, b/c it can be eaten anytime of the day, warm or not. I usually make it with whole wheat crust to make it a bit healthier.
Another standby is turkey meatballs (with pasta, which I usually bring uncooked).
Soup was also really wonderful and easy to freeze if we had a lot, which we did!
Enchiladas and Lasagna were nice too, but apparently quite a few people who brought us meals thought so too. So yeah if you can find out what other meals they are getting so you can change it up that would be nice.
Little extras like nice bread, muffins, little treats were also nice.