Check the Winter Cycling forum at this site. Lots of good information there.

I live in an area (NC) with a moderate climate, so winter is no big deal. What I dread are the 100+ days we sometimes get this time of year. My typical morning commutes in winter (Jan-Feb) are in temperatures ranging from 15 to 35F. That is very easy to dress for, but you do have to spend some money on clothes. Layering is the best way to keep warm, and has the added advantage of allowing you to shed layers as it warms up. Hands and feet are usually the soft spot -- invest in some good gloves, probably at least two pairs for varying temperatures and conditions, as well as some toe and shoe covers and wool socks.

Fogging is a real pain, and a problem I have not yet solved. I did buy some new Transition lens eyeware last winter, so I only need one pair of glasses for riding in the dark and light. You need glasses with good eye coverage in winter or your eyes will tear up on every downhill. There are various sprays you can put on lenses to prevent fogging, but I haven't tried any of them yet. That will be my big project for next winter as I'm pretty well covered with regard to the rest of my gear.