One certainly can't let winter weather get in the way.
My real problem has always been my hands. Especially on a short commute when I don't have time to generate body heat.
Most recently, I've been using Pearl Izumi Inferno Gloves. They're ok, but sub 20 degress, they don't do it, particularly since I like riding the hoods where I'm right up against cold metal.
Last year, my wife made a wonderful discovery....
Moose Mitts!!!! They velcro on over the handlebards. You stick your hands in when you ride.
This year, AMF Threadworks designed a set that fit on drop bars. Two weeks ago my set arrived!!!
Last week we were consistantly 20 degress or below in the mornings, I used these $10 hytrel gloves from campmor:
If you ride in the cold, check out Moose Mitts!!!!