This summer I'm planning on playing with some eco-friendly yarns. I've already ordered some Pakucho naturally-dyed cotton and several colors of hemp. I'm also really looking forward to trying bamboo, soy silk, and Vermont O-Wool. I'll probably try to do colorwork with them all with varying degrees of success. I've found the Green Knitter web site very helpful and educational with info different methods of yarn production with links to many environmentally-friendly companies.
Speaking of ecological knitting, here are some market bags I knit years ago from long-gone patterns. The one on the left is knit from thick cotton and much too big to be useful. Once you sling it over your shoulder and fill it up the bag will drag on the floor unfortunately. The one on the right is knit from Euroflax linen and much stronger than it looks. Both have been retired from use as a result of stretching and are now used to hold my various handknit items. I will probably make a few more (possibly from THIS free pattern) when my new yarns arrive.