The Soaring Safety Foundation (http://www.soaringsafety.org/) is an arm of the Soaring Society of America. Its goals are to reduce the accident rate in soaring and to make soaring as safe as a sport can be. Below are direct links to some of the more important articles from the SSF website.
Bronze Badge study Guide
Collision Avoidance
Current vs. Proficient
Premature Termination of the Tow
Ten Steps to Safer Soaring
Tow Pilot course
Wing Runner Course
Flight Safety Videos
Safety Officer Training Guide
Soaring Safety Foundation on YouTube
SSF Glider instruction
https://www.soaringsafety.org/learning/FSvideos.html