I popped into H&M yesterday and spotted a few breastfeeding friendly (but also cool if you aren't breastfeeding) items that i'd thought i'd share.
The high neck dress isn't usually a style that you can breastfeed in but this one has buttons down the front that would allow for access. Personally i would wear a thin vest underneath in one of the colours of the dress that i would pull down under my breast and that would keep my tummy hidden.
H&M do great thin strapped, in-expensive vests in loads of different colours - these are so useful for wearing under your normal t-shirts, tops, shirts etc. They have recently launched a longer length which is even better as it would come down and cover your waist. This style vest would also be great if you are pregnant as it would easily cover your belly and could be worn in the same way - under many of your existing tops.