Like tsl I'm a year round bike commuter (but not otherwise car free) and have been since September 2007. I'm lucky that we have more temperate winters in the DC area. The first winter I balked at riding a couple of mornings after having to deal with unforecasted sheets of ice on a commute home in early December. Since then I have not missed a bike commute for weather related reasons.

Weekends I will also get out and do some longer rides, some events, some group, but mostly solo. I do find I'm less motivated to get up early on a Saturday morning on cold wet days for a solo ride, and those are the days I'm more likely skip.