Tips from Winter Cyclists

Winter biking essentials:
Willingness
Waterproof, wind proof outer jacket (does not need to be insulated--you'll generate plenty of warmth)
Warm, waterproof glove/mitten combos that do not compromise your dexterity
Warm, waterproof shoe/boots with warm socks and room for toe wiggling
Warm, but thin head covering that will fit under your helmet and protect your ears
Wicking base layers, like silk or synthetics
Weekly chain lubing
Worn brake pad replacement
White headlight, red backlight and reflective tape. (OK, folks get by without these, but I think they help a lot with visibility)

Non-essentials, but darn helpful:
Fenders
Waterproof, wind proof pants
Armpit zippers in the jacket to help prevent overheating
A sense of adventure

http://www.bikewinter.org/tipsAndResources/ginstips.php