I went out yesterday -- North Jersey -- temp was about 22 Fahrenheit, I did about 20 miles. I wore mid-weight synthetic socks without any type of cover on my shoes. Padded shorts underneath mid-weight tights. Silk long sleeve base layer and mid-weight wool base layer, topped off with wind-blocker fleece pullover -- the wind block is on the front only. I used a behind the head type fleece earmuffs -- no cap of any type, and no cover on my helmet either. On my hands, I wore fleece lined leather gloves.
I was cold for about the first mile or so, and then I was comfortable with the exception of my feet, which were a bit on the cold side, and only really became a problem as I was nearing the end of my ride. By the time I returned home, my back was ever so slightly damp, but not wet by any means. My biggest complaint about cold weather riding is the snot control problem.
I enjoy cold weather riding because I can actually get the bike path in the local park almost all to myself. Yesterday I only saw 4 other riders, and they were all dressed like goose down mummies, in addition to a few hardy joggers. I also enjoy the looks I get from cagers when I'm riding in the cold.