Spinning sock yarn is a combination of choosing fibers and spinning fine.
Some tips for finer spinning -- adjust your draw-in on your wheel to be minimal, so that you could actually pull the yarn off the bobbin if you wanted to, but it still draws in freely too; use the best prepared fiber you can, i.e. it drafts easily with no sticking or grabby spots; use the highest ratio on your wheel, so you can get twist in quickly.
On a spindle, I typically use a 0.9 - 1.1 ounce spindle for sock yarn singles, and that weight or heavier for plying.
If you have a Louet, one way to reduce draw-in that's fairly specific to them is to "lace" the yarn back and forth between the hooks on either side of the bobbin. This reduces draw-in (it also cuts down how full you can fill your bobbin, though). Louets have hooks on the same "face", so the lacing is all on one side; most other wheels put their hooks on either face, if that makes sense in words ...
For more tips on fine-spinning see How can I spin fine yarn?
As well as several entries on my escapades spinning sock yarn.
I've spent the morning (ok, not all of it!) on flickr looking around at the variety of spinning/knitting groups -- and wa-la, there's one on sock knitting (of course!).
I've been very pleased with my sock spinning lately -- my really tight 3-ply knit into lovely socks, though I had the tension on the sock machine looser for the second sock, so I'm worried it might wear through a little faster. Ah well, I'm one of those odd people that likes to darn socks so I will get to indulge myself there. This was spun as a 3-ply very high twist, so it almost feels like cotton even though it's superwash merino. This yarn is now the socks shown at the top of this post :-)
And I've finished spinning my "just like Sock Hop" handspun, wow, the skein is very impressive! Can hardly believe I spun it.
(yes, it's the same colors as the skein above, but a squooshy 15WPI 2-ply as opposed to the above high twist 18 WPI 3-ply)
And I must-must-must get the socks knit soon, they will be sooo super squooshy.
Teyani (Intrepid Fiber Wizard) has posted a variety of entries on her blog about spinning the sock hop yarns from the Crown Mountain pencil roving (NAJAHC, yadayada), and her instructions were spot-on.
I've also been spindling yarn for socks ... that one's taking some time. I'm currently suffering from a variant of second sock syndrome -- the first sock-worth is spun, the second sock-worth is about 30% spun at this point. But, it's fun, and it fills the walk from home to busstop and back again with the kids each day. That first sock-worth is shown on-spindle in the picture.
Ahhhh. It's another skein I'm really, really thrilled with!
Well, now I'll go back to my more factual post-answers mode and stop sharing ;-) just couldn't resist.
I'd encourage folks to put their handspun sock yarn and handspun socks in the flickr group too :-) that way I can have google reader watch it and get my daily handspun sock yarn dose!
Looking for a place to chat about spinning sock yarn? Here are a few:
on Yahoo Groups: SpinToKnitSocks and sockamaniac_spindle_spinners
on Ravelry: STKS (spin to knit socks)
and I've seen sock spinning questions on Knitty's spinning forum as well as TechSpin (Yahoo Group) and Spin Tech (on ravelry).
Do you know any other places where sock yarn spinning gets discussed? I'm always on the look out for great websites and forums on the topic! Post them on the blog or contact me. Thanks!