The American Canoe Association
The American Canoe Association is the way to go if you're getting into boating. Their methods of skill progression have taken countless people from beginner to boatman.
Rescue 3 International has been setting the standard for technical river rescue since 1979. Their instructors teach in over 32 countries worldwide.
Sentinel Outdoor Institute
Sentinel Outdoor Institute provides Wilderness Medical training. They teach primarily in the US and Africa. They train at high altitude and river level and will help you prepare.