NORWAY:
Varsom.no (avalanche forecasts)
RegObs (registered snow observations)
The regobs-app (app for shareing avi info)
Skredkart (map with inclination over Norway)
Norgeskart (map that shows trails and calculates trip length + inclination)
SWEDEN:
USA:
Avalanche.org (find all avalanche centers here)
By state (in alphabetical order)
Arizona:
Kachina Peaks Avalanche Center (Flagstaff)
California:
Central Sierra Avalanche Center
Eastern Sierra Avalanche Center
Colorado:
Colorado Avalanche Information
Idaho:
Idaho Panhandle avalanche center
Montana:
Gallatin national forest avalanche center
New Mexico:
Oregon:
Central Oregon Avalanche Association
North East Oregon, Wallowa Avalanche Center
Utah:
Washington:
Wermont:
Mount Washington Avalanche Center
Wyoming:
Bridger-Teton National Forest Avalanche Center (Jackson Hole)
Other useful links:
CalTopo – Topographic map tutorial here
Wasatch Backcountry Skiing – interactive map
CANADA:
Most avalanche centers can be found at Avalanche Canada
EUROPE:
Most avalanche centers can be found here
JAPAN:
White Heat Project 