Andy Mark supplies industry standard hardware and equipment that is legal for use on the FIRST Robotics Competition robots.
In addition to supplying equipment for FRC robots, VEX produces an educational robotics kit for PLTW HS Engineering classes along with a version that is more suitable for younger students. VEX runs competitions for each of these product lines as well.
An innovative company that designs embedded solutions for robotics applications, Cross the Road produces many controllers and devices that can be used in the FIRST Robotics Competition as well as in other applications.
McMaster has an easily searchable, thorough supply of the key fasteners, stock, and equipment used in fabrication of mechanical projects.
Another great robotics supplier, Bane Bots has a selection of wheels with a variety of Durometer values as well as motors and other equipment.
Local to Tehachapi, the Composites Store supplies materials for composite fabrication across the country.
A great supplier of electronic components for hobbyists, Spark Fun is easily searchable and has project ideas for varying skill levels.