It's very difficult to find sock yarn when you can't tolerate animal hair. I keep queueing socks, and then not being able to make them because of this. There are some sheepless sock yarns, but normally you have to import them.
Lo and behold, sheepless sock yarn from the UK! My etsy persusals have final yielded fruit, and I now own a skein of YarnAddict's Organic cotton sock yarn (55% organic cotton/45% Tencel) in the Fresh Water colourway. I am being very restrained and not casting on inmediately, but that is mainly because I have only one skein and many sock pattern ideas.
I'll let you know how it knits up (it's very recent, I had to enter the yarn into the Ravelry database), but I'm very very excited about this!