Bamboo's nice; it knits up with a drapey but slightly "crisp" finish. I've also worked with soy "silk," which is softer and just as drapey, and am currently knitting a long wrap in a wonderful rayon-flax blend from Blue Moon Fiber Arts (http://www.bluemoonfiberarts.com/home) (the "Socks that Rock" people) that's just wonderful to touch. All share the same knitted-in-a-tube construction as the corn and bamboo yarn; they're a little splitty if you work with very pointy needles, but not too hard to control.

IANA vegan, but as much as I love knitting with wool, I have a hard time wearing it next to my skin (except as socks), and it's too warm for the climate here most of the year, so I've been playing with all the plant-fiber yarns I can lay hands on.