Bicycling has a nice article up on winter weather mountain bike gloves. They have put together a collection of the best options out there. There are quite a few models I was not aware of.
“The key to finding the right pair starts and ends with fit. If your fingers are smashing into the tips, or your knuckles get pinched when you wrap your hands around your grips, your hands will get cold.” – Bicycling
If you’re looking at buying some gloves online I suggest checking out Jenson USA’s cold weather gloves as well as Competitive Cyclist’s vast selection.
Wish I could find a US glove maker
I found these gloves to be US made:
http://www.defeet.com/men/accessories/gloves/