YAS (Yoga and Spinning) just sent me this Skull Tank Top to use for Yoga and Pilates. It's got a V-back, with adjustable straps, and the scoop neck covers you up. Personally, I hate it when my boobs pop out while trying to do Down Dog.
I have to say that the wicking fabric is super soft, and there is a generous-sized shelf-bra inside that offers support without too much constriction.
It's honestly one of the most comfortable tanks I've ever worn, and it's not too expensive either, for yoga gear at least. Buy it online at go2yas.com for $41.50.
I'm just not too sure about the morbid skull design. What do you think?