The ECO Pneumo Dry Sacks, designed to keep your clothing and other personals dry when you're out in the field, are made from a non-dyed, single-coated "bamboo-based fabric" along with a recycled aluminum purge valve. I have no idea how well they work; I just think things made out of bamboo are interesting.
They again, they're priced from $30 to $45, depending on size. Seems like a lot of money for a dry bag. Maybe someone could make one out of cheap, disposable plastic?