I'm looking out the window at big flakes of snow falling out of the sky and blanketing the ground. In mid October, this could be a fluke or the real thing. That's what makes living in Minnesota so damned exciting!
In any case, contrary to popular belief, winter is a great time to ride your bike. And if you're going to do it, riding on studded tires takes away some of the risk and uncertainty about riding on icy streets, or streets that appear to be clear, but have hidden patches of black ice...
And studded tires, we got 'em now, but don't expect to find them in December:
Hakkapeliitta W106 700x35
Hakkapeliitta A10 700x32
Either is $50/ea or 2 for $90
If your bike can fit 'em, get the W106. If a generously sized 700x35 doesn't quite fit, but it's close, the A10 should work. The A10 has fewer studs, and less aggressive tread, but it's probably your only choice if clearance is a concern. Nokians are tough and durable, but also somewhat heavy and ponderous. If you're looking for a lighter, faster, but still plenty studded tire, and/or one that has a reflective stripe, scroll down to the Schwalbe section.
700x35 or 26x1.95 $65/ea or 2 for $110
The Kendas are similar to the Nokians. We have used/sold both, and consider them to be more or less equivalent.
Schwalbe Marathon Winter 700x35 or 26x1.75: $80/ea or 2 for $130
The cream of the crop of studded commuter tires is the Schwalbe Marathon Winter. I rode the 26x1.75 version all last winter, and they almost felt like normal, non-studded tires when I was riding on dry pavement. Very smooth rolling for studded tires. They cost more, but they are lighter, yet have more than 2x more studs per tire (it boggles the mind) than the Nokian Hakkapeliitta. They also have a reflective sidewall, which comes in handy if you're riding outside of our 8 hour period of daylight in the winter. I can't recommend this tire enough.