It's a few degrees below freezing here now, and I ride with a microfiber Buff pulled over my nose to heat the incoming air. It gets all soggy after a while, though.

Anyone try something like this?

http://www.teamestrogen.com/products.asp?pID=21626

I found something very similar in a bike shop yesterday, but it kind of freaks me out. Looks like it might stay dryish, but then, you can't pull it up and down to adjust as you go.