I rode all of the last three winters. Actually, I was in Colorado this past winter when things got rough, but I spent January-March in the Northeast. I rode in the sleety-rainy-ice-storms, the blizzards, the dry as a bone frigid days, the windy days, you name it. Snow thunderstorm 2011? I rode.
When the Northeast had that big cold spell this year with back to back days at -15º, I rode in a synthetic puffy, a thick fleece, and a raincoat (wind blocker). For my hands, I used expedition-weight synthetic fill mittens, which badly need replacing, but I can't find a suitable replacement (they were basically puffy jackets for hands, no heavy leather reinforcement or waterproofing BS).
It basically went like this:
Midweight Merino Top
Thick Fleece
Synthetic Jacket
Raincoat
That was the worst cold ever. Most "regular" cold above 10º, I just wore the fleece and maybe a softshell. Softshell is very good for non-extreme cold as an outermost layer because it breathes without letting the wind in. My Rab Zephyr softshell weighs like 6oz.
For my legs, I wore a wool baselayer and windproof tights underneath a rain shell. I also had knee warmers, but mostly didn't need them.
For feet... tricky. I basically failed, because I got frostnip twice last year when I climbed the local peak (Mt. Greylock). The ride down would freeze my feet well past numbness. At the peak of the season, I was using my summer cycling shoes with neoprene toe caps, light wool liner socks, and gore-tex outer socks, and a warm wool baselayer around my ankles. This year, I'm experimenting with fleece-lined neoprene socks instead of gore-tex socks. If I can't get enough warmth out of my socks and still fit my foot in the shoe, I'm getting overboots. My previous system worked under 10 miles, but my Greylock loop, which I can usually do right up until the end of January unless we get unlucky snow, was like 30 miles.
I picked up a cheap pair of ski goggles from a friend for like 5 bucks. They let me wear a full-face balaclava and still see. A little wicking liner hat kept my sweat from freezing, though I still got beardcicles every ride.
Riding all winter is not just possible, it's a blast.
Here's my winter touring gear list (FIXED!)