AD Boivin - http://www.adboivin.com/
Snowmobile provider with Polaris, Yamaha, SkiDoo, and Arctic Cat models. French based with English website option.
ATK Motorcycles - http://www.atkusa.com/
Provides off road motorcycles for the American market and also provides spare parts as well.
Snow Groomers - http://www.snowgroomers.net/
USA site that focuses on cross country skiing, snowshoe trails, and sled dog trails and provides equipment.