Here's what I wore yesterday for an extended 10F ride w/ 30mph winds:

Feet:
- Wool hiking socks
- Bags over feet
- Cotton socks on top to hold down the bags

Lower:
- Biking shorts
- Polypro longjohns
- Snowboarding pants

Upper:
- Wool T-shirt
- Light ski jacket

Hands:
- Leather gloves with synthetic wool lining

Head:
- Stocking cap
- Neck gaitor

Kept me toasty warm. We went inside at one point and I took off my coat and cooled down quite a bit so I threw on a wool sweater and left it on under my coat when we went back out.