I happened across the KtraK kit in my eternal quest for bike lore. This would be just the ticket for people living north of the Arctic Circle. (For the rest of us, it seems like a waste of money, since the snow will soon be all melted.)
(I know some of my readers are major gear-heads... y'all oughtta love this thing! Clancy can prolly build his own from spare parts in his garage; Danielo will fabricate one out of bamboo!)
The kit is supposedly now available for 26" bikes. Here's the manufacturer website. (Direct from them, the rear kit is $519; the front ski kit is $169.)
If it really works, it's prolly just a matter of time until there are hot-headed conflicts between cross-country skiers and kamikaze downhill KtraK riders!