Video clips of avalanche incidents which is available on-line. Also check archives of local television news stories (stations in Western states and Provinces) regarding avalanche incidents and fatalities.
Sawtooth National Forest Avalanche Center (Idaho)
www.youtube.com/view_play_list?p=797B0F7F3CA894C7
Youtube
https://www.youtube.com/results?search_query=snowmobile+avalanche+safety
Gallatin National Forest Avalanche Center (Montana)
https://www.mtavalanche.com/education/tutorials
Northwest Avalanche Center
http://www.nwac.us/education/resources/
Utah Avalanche Center
Stability tests, non-standard – https://utahavalanchecenter.org/education
‘A Dozen More Turns’
A powerful documentary; while ski-based, the backcountry decision-making lessons are also pertinent to snowmobiling.
http://lifeonterra.com/?s=a+dozen+more+turns