+1 on the Smartwool. They aren't cheap, but they are super comfortable, warm, and naturally stink free. I went on a three week backpacking trip through Europe this past fall and regularly went three days straight in the same socks without them getting stinky. Mind you, we walked a TON on that trip. I have smartwool socks for casual, backpacking/hiking, and cycling. Can't recommend them enough.
As far as synthetics go, they may be warmer when dry, but as soon as they get wet, you may as well not be wearing any socks at all. Even when wool is wet, it'll keep you warm.