I ran across this at www.yourguidetogreen.com.

Pack cloth shower curtains are a durable, hassle free alternative to vinyl. When cotton or hemp just won’t do, pack cloth is your best choice!

Pack cloth is a very special, urethane-coated nylon fabric with no out-gassing and no readily discernible smell even when new. It's a highly durable, ultra long lasting, man-made material. Highly tear resistant, it won’t fray, fade or bleed. So light, it’s like the caress of a spring breeze. Best of all, pack cloth is unaffected by mildew or rot! Works great as a liner, too! And there’s more! Though machine washable (in cold water), it'll rarely need it since pack cloth naturally repels liquids, dirt and other grime. A damp cloth or sponge is usually all that’s required for easy clean-up!

What do you think about this?

I have a heavy organic cotton shower curtain. After a shower, I spread out the curtain as far as it will go and let it hang to dry on the outside of the bathtub. I've never had a problem with mold or mildew.

We had no problem with mildew on our cotton shower curtain. I did wash it occasionally - maybe once a year. Our summers are sometimes humid, but we generally run the A/C during those times anyway. We had 2 adults using the shower. In a different climate, or with a large family it might have been different.

Our current house has a walk-in shower, but the cotton shower curtain now hangs in our guest bath.