Probably Duofold brand. They have a cotton interior, with a wool exterior. I haven't used them in years, but they're quite warm. Too warm really....
Edit:
I overlooked the camping part. Your best bet is multiple light layers. Use the typical WalMart longs, and wear a Tshirt, long sleeve shirt, sweatshirt, vest, and jacket with it. That way you have a lot of air space for insulation, and you can micromanage the warmth, and shed layers if you get too hot.