For cycling in cool to cold weather, the right sort of wool cannot be beat. For racing you will want pockets, or fancier fabrics, or some other thing, but for riding for transportation any decent wool will do -- which can mean your daily gear will be a lot cheaper and easier to come by, too.
There are a few companies making decent wool for active uses -- Smartwool and Ibex are the first two that come to mind. Others make cycling specific wool -- Wabi Woolens, Portland Cyclewear, Surly, Swobo, Santini, etc... for just plain longsleeve wool jerseys with a zip neck, Smartwool can't be beat. The Ibex stuff is excellent, but the Smartwool baselayer is thinner, while being no less sturdy. And cheaper in cost, too. Find one at a TJMaxx or Marshalls and it'll cost you 20-odd dollars instead of 50-70 dollars.
But even at list price they are still cheaper than the hundred dollars or more paid for cycling specific wool longsleeves. The only disadvantage is lack of pockets and usually lack of color. Smartwool does offer a red version, but all I found were black and olive drab. Not a bad deal, though; you'll be wearing something -- a shortsleeve cycling jersey or t-shirt, a vest, or a jacket of some kind -- over this, probably, so it by itself doesn't need to be too bright for the cars. And a jacket, vest or jersey will usually have pockets. Plus, dark colors don't show dirt as much, which is an adcvantage as wool doesn't have to be washed that much any way.
One of wool's advantages is it doesn't stink up as quickly as synthetic fabrics do or stay sweaty like cotton tends to. To test this, I took the first of the three Smartwool longsleeves I got (one olive drab, two black) and wore it (the olive one) for a week and a half straight. Without washing. That's riding my bike to work, riding to the bike shop to hang out, and to an impromptu party we had behind the bike shop on Sunday.
I sweated in it while riding with a jacket over it, I ate with it on, hung out with it on, drank beer, then later woke up, put it back on, rode to work, had coffee, and I stashed it in my messenger bag rolled up while at work. Wearing the wool allowed my to ride in with only a light jacket or windbreaker, or unlined rain jacket, this past week -- and ride home in just the wool and a jersey if the weather warmed up, as it did. So rather than take a warm jacket for riding into work in the morning, and a lighter one for riding home, I just wore a lighter jacket over the wool and stashed the jacket for the ride back. After all this it doesn't smell, not is it much the worse for wear -- no holes or tears.
As stated, this wool allowsd you to layer good. I could wear it next to my skin -- it's a baselayer -- but i typically wear a sleeveless shirt or t-shirt type shirt underneath, of a thin breathable fabric. Then I wear the wool, and then either a jacket or a -shirt or jersey, short sleeve. The short sleeve jersey is usually brighter so it helps me be seen more than black or camo colored wool would, if I wore the wool right on top.
At the end of the day, this thing is comfortable from the 30's up into the 50's, and if you have to do a lot of local trips on your bike, stopping at the store, bank, etc., you won't cook while waiting in line -- it can handle indoor temperatures too, unlike some winter bike gear which feels like a hot tub after 5 seconds indoors. Also good for varying conditions purely outdoors, too.
Anyone who bikes for transportation should have one of these -- or something like it.
