The acoustic guitar construction video course was THE resource for me in learning to build. He goes through each step completely and explains the reason for tool choices, troubleshooting, etc. Many other courses also available, including guitar finishing, etc.
Another great online resource. They have more general instrument parts, but also have a great selection of tools and woods.
Allied Lutherie
Tonewood
Advanced Shell Technology
Flexible shell strips for inlay or purfling
Alaska Woods
Tonewood
Driftwood Guitars
Amazing YouTube channel with lots of guitar building insight and even more amazing guitars.
Curly Maple Wood
Source for flame maple and other exotic woods for binding, etc.