I haven't used bamboo or soy but I have used corn yarn. Nice to work with -- like a wonderful cotton. I actually used it for dishclothes and they are very soft and launder nicely.

Cathy

Soy and bamboo make wonderful soft socks!

Tami

I'm just finishing a pair of soy/wool combo handwarmers, the yarn is very soft and seems to wear well, according to the washed and dried swatch. A friend knitted a pair of bamboo-cotton combo socks for me and I love them (the yarn is called Panda Cotton, there is also Panda Wool)