I assume whenever I see this question what's really meant is areolas which I, too, am too much obsessed with. One of my little dreams is that I would see significant growth there (not so worried about the nipples themselves, that will probably work out fine)
I'll be looking into some of the tips mentioned above but as another thought - I have read that it is possible to have a matching colored tattooed around the areola which will create the illusion of a larger size.
Not sure how reliable that claim is or if there's any downside.
also, a bit off topic - CHICKEN FILLETS?