I like the Maggie's Organics socks that Mom has sent for Christmas over the years -- a bit pricey for me, but when it comes down to it, they're my favorites, so good value. (I've got the tie-dyed ones on now - the fuschia tops go with my bathrobe and it's cheering to a sickie...)
Looking at their selection, I guess the ones I have have 10% nylon, along with the spandex in the top. They do have some 99% cotton ones. They have this testimonial on that page: "So I have discovered something, the Maggie's socks are EVEN MORE awesome after washing them!!!! Ahhhhh! True love! - Lauren, MI"