Fortunately, a few companies out there are making use of what's available to us here on our fine planet and developed some great, natural fiber athletic apparel. One of my favorite "fabrics" for working out is merino wool. Here is a great write-up on why "All you need is wool", from Rivenndell Bicycle Works' awesome website.
I have to make the disclaimer that one of my best friends works for Ibex, and recently opened their flagship store here in Boston. Still, I have to say, their products are absolutely beautiful, well-cut, and comfortable, and they work. I ran a race in 35 degree weather in October wearing only the Woolies crew under the Zephyr zip up. I was totally warm, comfortable and dry. I also think that Ibex's products are great looking and function as nice layers even if you aren't exercising. And as a tall person, I love that they are cut longer. I have yet to wear any of their merino wool t-shirts or tanks for yoga or to run on a warm day (it feels weird to even type that), but you have to figure that if this is the same stuff that keeps sheep warm in the winter and cool in the summer, it should work for us, too. Here are a few of my favorite Ibex picks.
Another company that uses not only merino wool but bamboo, is New Zealand-based Icebreaker. I may have to order some of these tops. I love these colors and think that v-neck tops are flattering and can make you feel sexy when you're working out. There's nothing wrong with a little sweat shimmering on your chest when you're at the gym. Yep, I said it.
Alo makes a lot of their clothes with recycled material like bamboo. I got this great Alo pullover at City Sports not too long ago, and they have some other nice things on their website like this yoga top. It is made from 67% bamboo, and I think the color and cut are really pretty.
Hope you do something that makes you sweat this weekend!