What is the best underwear for cold weather riding? I've been happy with Under Armor style shirts, but haven't found any pants that work well for cold weather. I'm not going to pay $50 just for the Under Armor name. Any suggestions for warm pants to wear under my jeans to keep the cold at a minimum?  

my suggestion would be to skip the underwear and buy a pair of snowmobile pants.i got a pair at Wal-mart about 5 years ago for $20.make sure you get them in a size larger than you would normally wear.i think mine are XL.if its really cold,im talking 0 degrees i put a pair of exercise pants over my jeans and then the snow pants.with 3 layers that keeps alot of heat in.  

HI I agree with 999. That is what I did i went a bought a full snowmobile suit for about 30$. Get the XL or bigger so it will fit with all the other stuff you have on..Now I ride nice and toasty when it is cold out...scruffy  

Actualy you would be surprised how warm a set of chaps will keep your leggs. I have a set thats lined and they work great.  

I've ridden in active snow, and I'll tell you, the basic long johns (you know waffle weave and all) are going to work as a base layer. Jeans over that, and then something with protection from road rash, and wind, and you're good. Toss a couple of charcoal heaters in the boots to warm the blood before it goes back up.

The high tech fibers (which I own a lot of, because they work) are not needed on the bike. You aren't doing much exertion, if anything, you have a risk of hypothermia, not drowning in sweat(at least in context).

For Skiing, I got a set of P51 pants that are windproof for $30. They'd work, but, I already have a pair of Tourmaster pants that are windproof, waterproof (mostly), and enough material to ride out a skid.