Here is a page dedicated to useful resources around the interwebs. Enjoy! The links with an asterisk are resources that are especially pertinent or helpful. For further reading, we highly suggest you check out those links.
Official FIRSTInspires Resources
General Team Resources
Building Resources - Principles
Building Resources - Applications
3D Printing Practical and Safety Course - Tom Bladykas, FTC 3736
Building Resources - CAD
Guide to Rendering in CAD - Justin, FTC 9656
4137 Islandbots Library of goBILDA parts in Fusion360 format:
Building Resources - Calculators
HTD Pulley Generator - Henopied, FTC 18255
HTD Belt Generator - Jeremiah, FTC 10641
Coding and Software Resources
Java Workshop - FTC 4613
OpenFTC (useful programming tools)* - 4634 FROGbots
Editable Control Award Document - Ryan, FTC 1002
The FIRST Tech Challenge Discord server is a discussion-based community server that has teams ranging from first-year rookies to Winning Alliance Captains at the World Championships. It also has a channel for direct access to vendors.
FIRST Updates Now provides FTC/FRC related content including recaps, shows, analysis, reveals, and top 25.