Bamboo is lovely and soft when used to make bath towels, socks and sheets, so I can't imagine a better fabric to have intimately acquainted with one's nether regions!
These boy-cut undies from League of Lovers and Thieves are not only unusual in being made of bamboo; they also have a very interesting 'vein' design on the backside (and there's even a 'human heart' tank top to match if you're into your anatomical motifs!). If that's not for you, the Canadian-based company make a wide range of other bamboo garments, and ship all over the world. See this earlier post to find out why bamboo is so amazingly good for the planet.
From: Green graffiti - It's all in the mossage