I'll dog pile onto Exciteable's (also Mark Twight's) layering system. My goes:
Top half:
Spandex
Windshirt (it's amazing the range of temperatures this one two combo can handle)
Soft Shell
Fleece
Puffy (only in camp or @ pronlonged stop)
Bottom Half:
Spandex
Hard Shell
Puffy (works surprisingly well over hard shell pants when its really cold-or in an underwight sleeping bag)