When I first was pregnant with my first child, I bought a bunch of nursing tops from Motherwear and One Hot Mama. Only a few of them survived; the rest went to the thrift store, or to friends who liked them better than I did, as soon as I had a chance to try breastfeeding in them.
The first style of nursing tops that I decided I liked was called the "Super Secret" nursing top, and was sold at One Hot Mama. They still have some tops that bear that name, but the ones I used back then were different: they looked a lot like twin-sets, except that the "cardigan" was attached to the "tank," and the openings were sort of under the arms, hidden by the cardigan part. I thought it was a pretty ingenious design, because the opening wasn't obvious. I liked that, since I was going to school at the time, and didn't always have the baby with me to carry in front of me and hide the nursing openings (the way the annoying models do in the catalogs of nursing tops — hello, WE WANT TO SEE WHAT THE SHIRT LOOKS LIKE.)
I also liked the "all-around crop top" style of tee shirts and turtlenecks, where the whole shirt had two layers and the top layer lifted up all around to allow access to the layer underneath with the openings. Mostly because I could tuck the bottom layer into your waistband, and thereby keep from exposing your belly flesh to Minnesota winter winds. One of those crop top tees, a black one with the One Hot Mama label, I used for eight years straight and didn't get rid of until I lost a lot of weight and it didn't fit anymore. It was one of my favorite shirts.
But the lots-of-nursing-tops phase didn't last long past my second baby, after I was done with school. I figured out that it was easier and cheaper, most of the time, just to wear any old knit top. As long as it was loose and long enough, I could just lift up the shirt for the baby and still nurse discreetly enough by tucking the extra folds of the material around his face. I was heavier then, and I wore a lot of loose-ish, long-ish tops. I still used nursing tops and nursing dresses just for Sundays and nice restaurants, when I didn't want to look too sloppy. Since they were my "nicer" clothes, and I had fewer of them, I was willing to spend a little more. For those dressy clothes, I love the Japanese Weekend label (hint: as soon as you get pregnant, check their out-of-season sale, which will be in season by the time you are big), and hands-down my favorite design for nursing openings is made by Boob Nursingwear. It's especially good for a dress.
This time around, though, I've settled on an entirely different strategy. Probably because, being a lot slimmer, I'm not wearing so much loose flappy stuff on top, and I find that in the trimmer and more fitted stuff I'm finally able to wear, I can't really nurse discreetly just by lifting up. I'm also kind of loath to invest in a whole new wardrobe of nursing tops, which aren't cheap anyway, after having had The Year Of Three Wardrobes last year (an entire, if abbreviated, wardrobe in size 6 or so; an entire, if abbreviated, wardrobe in size 2 or so; and a maternity wardrobe). I am willing to wear a stretchy-necked or button-front dress and go down through the neck if I am at home or among friends, but not out in public.
So I've taken to wearing an inexpensive cotton v-neck camisole, slightly too small. The kind they sell at Old Navy or Gap Body go on sale for five to eight dollars. I adjust the spaghetti straps so they are a little too long, and tuck the camisole into my waistband. Then I wear whatever ordinary top I want to wear over that. When it's time to nurse the baby, I lift up the top and pull the camisole down out of the way, and open the nursing bra. I find that the combination of (say) a trim tee or knit top that covers my shoulders and chest, and a camisole that covers my belly, plus the added coverage of a sling, is really effective at minimizing exposure. Except, of course, for the few seconds it takes to get the baby latched on, but I don't really care about that; it's over quickly.
I think a large part of the reason I'm so much happier with the camisole strategy is that it thoroughly hides my squashy mommy tummy, which has gotten even squashier after the weight loss. Further evidence for my theory that different body types require different strategies of nursing clothing.
I still want a good nursing dress in my current size, but I despair of finding one I like without being able to try it on.