This site links to all local forecast centers, archived accident reports, and a spiffy state-by-state avalanche-course locator.
The U.S. Forest Service runs users through an interactive backcountry tour, gives an avalanche-science primer, and provides links to SNOTEL graphs of snowpack characteristics.
The Canadian Avalanche Association provides satellite weather feeds, regional discussion boards, and timely academic articles.
Snow Sense: A Guide to Evaluation Snow Avalanche Hazard by Jill Fredston & Doug Fesler
This 120-page field guide - loaded with practical bull's eye clues to snowpack stability, tips on weather analysis, and hazard checklists - is tiny enough to carry with you. ($9)
Staying Alive in Avalanche Terrain by Bruce Tremper
A 284-page tome, written by the director of Utah's Avalanche Center, this is
textbook for course instructors. ($18)
Teton Gravity Research and Backcountry Access team up in a 30-minute how-to video for the BCA Tracker DTS, the most popular beacon in North America. ($10; bcaccess.com)