structure could be something like a directed acyclic graph (a DAG) in order to hard-wire dependencies*. Contributors need to be able to add a) learning resources and b) appropriate project/s which assume ONLY previous projects done at each node.
Question: Should the resources on a given node be the resources to get TO or FROM that node? In other words, how to make plain what's needed for next step?
Classical Engineering (mechanical, electrical), Programming (command line [web, front end, backend, systems/SRE])
Web front-end for contributors - at the very least, a ratings system for resources. This will trend heavily toward the bottom of the tree.
Bigger idea is for an interactive webapp with achievements, exams, and probably some games between, or as part of a large game.