Before fat bikes (like the Pugsley) were invented, people used studded tires on regular bikes for riding in snow. I know some people who have made studded tires for their mountain bikes (using a tool to poke holes in the tires and then pushing screws through them, sharp end out). I assume you can also buy studded tires. A friend recently posted a photo to facebook showing his bike -- something that looked like a road bike, I don't know if it's a racing bike, touring bike, cross bike, etc. -- with a new SKS fender for the back wheel. He said he had studded tires on that bike.

The question is -- is it even worth the investment in the tires if you don't get snow that often?