I wear UnderArmor under my long-sleeved jersey and then a windproof jacket. I've got one from PI that is windproof, water-repellent and very lightweight (they say it'll fold into a jersey pocket!) For the bottoms, shorts, leg warmers, and Smart Wools socks. Below 30 I wear windproof pants and thermal bike gloves. Below 20 I wear toe covers, lobster gloves and a 2nd long-sleeved jersey or my arm warmers on top (depends on what direction the wind is blowing). Anything under 50 I have on my polypro blalclava as I have problems with my ears getting cold. So far I've ridden with wind chills down to 6 and temps in the teens and did OK. Like star said - if I feel overheated I just unzip my jacket a little or if need be I can even remove some of the layers. Its actually kinda fun riding in the cold - sort of a primitive "you and the elements" kinda thing! (but then I'm probably not normal!)