Hey nowonder - I've been wondering the same thing about riding in winter. I did some last year on my mtb and it wasn't as bad as I thought it might be. The key is to layer! Get yourself some good leg/arm warmers or tights and a good breathing but warm jacket. For all of this I highly recommend Pearl Izumi. Their stuff is a bit more costly, but it's very much worth it!

I think I'm also going to invest in a set of rollers with resistence fan. It evidently helps you define your pedal stroke (make it more efficient and "round") and improve your balance.