Something that freezes well--they'll appreciate meals down the road as well. Chilis, stews, stuffed pastas and lasagnas in small portions all work great. I cooked a bunch of these before my first baby and stocked the freezer--it was a great help!

I agree with Melissa -- a complete meal, down to the vinaigrette, is lovely. Our neighbors did something similar for us and we were so grateful to not have to think about a thing - just eating! I'd also add that a big carafe of freshly squeezed lemonade would be most appreciated, I'm sure, since mom will need lots of fluids. If you wanted to go beyond the basics, this strawberry-basil lemonade would be great: http://food52.com/blog/7046-strawberry-basil-lemonade

Poppy Seed Chicken is one of my favorite main dish casserole recipes to use for just such occasions. There are several good recipes for this on the Internet.

After I had my first child, many people brought us food. The one I remember, though, was the friend who brought us a meal. It was not fancy, but it was fantastic. She brought a green salad with carrots and peppers and cukes, pasta with red sauce (we just had to pop it into the over), a baguette with butter, and some brownies. She even brought vinagrette. It was one of the loveliest meals I've had in my life. I was learning to nurse, not getting much sleep, and incapable of putting together a complete sentence, but I knew a wonderful meal when I tasted it.

I would make some taco fixings. Lettuce, tomatoes, cabbage slaw with lime, chicken stewed with tomatoes, or maybe grilled it fried fish. These can all be made contained separately and a couple of packages of pre-cooked taco shells. Make enough for leftovers and bagged shredded cheese. No containers to pick up or for them to keep track of. It will be the kids favorite meal brought over.

Summer in the south says chicken salad to me! Here is a great one that you can prepare ahead and just assemble before delivering:
http://food52.com/recipes/13065-raspberry-chicken-salad-with-honeyed-walnuts-and-gorgonzola
(You can omit the red onion if you think if would be a problem for the new mother.)

Maybe a modified jambalya? With lots of tomatoes and the milder peppers (yellow and orange) and even some other veggies, maybe seafood, and a smoky ham rather than spicy sausage? And definitely agree about the big salad, and bread, and and maybe fruit for dessert.

Let your imagination run loose and try some rough n ready pesto with fresh summer ingredients. You can prepare in advance and then just add to good quality tagliatelle. Think pine nuts, lemon, grana padano and basil, or feta, walnut and mint. Both crowd pleasers in my book. Or peas, asparagus, mint, chilli and lemon.

You might even take them all the fixins for a big salad. People often take heavy foods, such as casseroles or lasagne, and I'd be willing to bet that they're jonesing for some fresh fruits and veggies. Maybe put together the components for a niçoise (steamed haricots verts, boiled new potatoes, boiled and peeled eggs, good tuna, etc.).

Quiche! Maybe a corn, cheddar, basil quiche?

I love cold soups in the summer - cream of zucchini, gazpacho, borscht, etc. - and they require no reheating, plus are generally better made ahead anyway. Grain salads also keep well and can incorporate lots of summer vegetables and herbs. Cold poached salmon with cucumber salad, also can be made ahead and requires no work before they eat it. A fresh fruit crisp (berry, peach, cherry...)One caution: if the mother is nursing, best to avoid hot peppers or spicy food. (A newborn eating pimento cheese, or any cheese? Surely you jest, Pierino?

There is that southern classic, pimento cheese. Spread it on Ritz crackers. The baby might be able to eat the cheese but not the cracker. Another one might be Missisippi tamales. They are long and skinny and you don't need to use corn husks. Parchment is fine for a wrap.

How about quiche? here's a good recipes:
http://food52.com/recipes/10180-beloved-greens-quiche Or meatballs and spaghetti; meatloaf; chili