When I'm spinning out on my 53x9, it means that I am cruising downhill at a pretty good clip.

But, my regular commute doesn't take me over that hill.

Each person will find somewhat different gear that is comfortable. The [MENTION=124426]Jim from Boston[/MENTION] list is a good start. I don't have studded tires, and can stay home if it gets too nasty out (no snow or freezing rain so far this year).

For seasonal cycle clothing, this time of year in the northwest, good rain gear is a plus. Rain shoes, rain pants, rain jacket. I also use the rain jacket as a wind breaker. Cycle Specific clothing is nice including good ventilation for the rain gear.

Spare Tube?
Also have a small stock of spare parts so one can get back on the road if something breaks. Redundant bikes?