I would also strongly urge you to just wear stuff you already have. For most commuters, this is not an extended trip through Greenland. There's a building on both ends with space heating and shelter.
Wost case scenario for me in DC, for example - Getting a flat with 6 miles left to go when the temp is 17F and I've worked up a sweat (which I almost never do by dressing properly). I keep those hand warmers used for hunting in my panniers and a goretex shell at all times, so that helps. I could walk the bike to a business or the subway, walk to work, call my wife, etc. I could make due and not freeze.
Leopard seals will not come for me.
When you consider this, you can basically throw all the "cotton kills" BS out of the window and just wear regular stuff. Don't overdress is the main thing. There's no need to stock your closet with all new clothes just for riding a bicycle in the cold, unless you just really like doing that.
Last edited by TurbineBlade; 10-29-11 at 06:28 AM.