American Institute for Avalanche Research and Education
AIARE multi-day avalanche courses form a unified training program, Level 1 through Level 3, that focus on decision-making and risk management in avalanche terrain. A 1-2 hour Avalanche Awareness course is also available. Courses are taught by "course providers" throughout the country. Be aware that not all the courses offered by the providers are at the AIARE standard.
www.avtraining.org
www.avtraining-admin.org/courseprov.cfm for a list of providers

Avalanche Danger Scale
www.avalanche.org/usdanger.htm

California Avalanche and Weather
Contains links to other centers
www.avalanche-center.org/Bulletins/Calif

Mt. Shasta Avalanche Bulletin
http://www.avalanche-center.org/Bulletins/Calif/shasta.php

Mt. Shasta Avalanche Center
www.shastaavalanche.org

Sierra Avalanche Center
Tahoe National Forest
www.sierraavalanchecenter.org

Eastern Avalanche Center
www.esavalanche.org

Avalanche.org
Includes links for many areas and other information
www.avalanche.org

National Avalanche Center
Includes links to many areas and other information
www.avalanche.org/~nac

Worldwide Avalanche Bulletins
www.avalanche-center.org/Bulletins