After searching around for some wool socks, I finally decided on these as $5 per pair was one of the best prices I could find.  These would be a bargain at twice the price.  They obviously keep your feet warm in the cold, but the real benefit is that they aren't TOO warm.  They don't hold sweat and bunch up as some thick cotton socks do in boots.  They fit great and stay in place.

I wear an 11.5 boot and had no trouble at all with the socks being too small or shrinking.  Wash on cold/cold and then hang to dry.  I assume putting them in the dryer would be a terrible idea, so I haven't done that and don't plan to.