Honestly, in the summer I've been wearing cotton. It holds the moisture more than poly, but for me anyway, it doesn't stink, and if the weather is warm it's not really uncomfortable.

I have alertshirts that I normally wear, but they get rotten smelling within an hour, especially in the summer.

I hear that wool is great. I'm just too cheap to buy it, and I have checked at the salvation army, and though they have literally a couple of acres of clothes, I have yet to find any wool other than heavy itchy sweaters there.