One of the concerns I hear most often is that women need more supportive sports bras in natural fabrics. While FaeriesDance.com has sports bras in organic cotton and bamboo, thus far they haven't rivaled their synthetic counterparts for really good support in high-impact sports. Last year I ran my first 1/2 marathon wearing the Bamboo Sports Bra, and while it was "good enough," I have to agree with my fellow sports enthusiasts that it could have been better. I also happen to be on the small side, falling between an A and a B cup. The C and D cups out there are really struggling to find something natural, breathable, eco-friendly and supportive.
Organic Cotton Sports Bra or even the Jen's Bra should work equally well as the bottom layer. The internal shelf bra in the layering tank fits a tad tighter than usual since it's now sitting on another garment instead of directly on the skin. That tightness helped hold the sports bra in place and provided a full second layer of anti-bounce protection. Almost any tank or cami with an internal shelf bra should work equally well, and as a side bonus, the layered look was quite attractive. I should warn that my cami got a little stretched, and while its still perfect for the sports layering, extended wear this way might make it less usable on its own.
Of course, we're still trying to find other options in technical sports wear. I've found some companies that have the right idea. One company is making technical sports bras out of traditional polyester, but using recycled fibers. At the moment, they're recycled content is only 35%, which doesn't quite meet our eco standards, but it's a good start, and we'll keep following them to see if they can pull off a great design with more recycled materials. But in the meantime if you need more support right now, just double up.