The best combination to protect your hands from winter cold is a pair of heated grips plus handlebar muffs. Most folks say you can then get away with just using summer gloves. A lot of people (self included) don't like muffs cos they look awful, but if I did have to do a regular winter commute, I'd fit them.
For the amount of winter riding that I do, I find the Spada Enforcer gloves quite good. They're a bit on the thick side, but I find I get used to that the first time I pull them on for the winter. I have heated grips as well, which make quite a difference in combination.
It will also make a difference to keep your body core nice and warm, this will translate somewhat to your hands. Use thin, warm layers, with a windproof layer, all under your bike jacket, making sure of course that you have a good waterproof layer in there somewhere for wet conditions.
Ok, positron beat me to it, but I'll post this anyway cos it pretty much underlines what he said.