The Chrysler Sno Runner looks nifty.
I don't know that the Ktrak bicycle thing would work so well really.
I've never tried one and don't know anyone else who has either, but when the pubicity of these things first got around online, a lot of bicycle-building experimenting people in northern climes noted that skis and drive belts ONLY work well when they're wide enough to float on top of new or deep snow--and even when they ARE wide enough, they have so much running friction that nobody much gets into riding such a human-powered vehicle, it's just too much effort.
If you are dealing with snow only a few inches deep or already hard-packed, then studded MTB tires generally work much better. They're not exactly inexpensive at around $100 each, but they are far more convenient and probably more reliable than the Ktrak thing.
~