LibreTexts is the adaptable, user-friendly open education resource platform that educators trust for creating, customizing, and sharing accessible, interactive textbooks, adaptive homework, and ancillary materials. We collaborate with individuals and organizations to champion open education initiatives, support institutional publishing programs, drive curriculum development projects, and more.

LibreTexts is the largest centralized open education project and platform online. Founded in 2008 at the University of California, Davis as the ChemWiki, the LibreTexts mission is to unite students, faculty and scholars in a cooperative effort to develop an easy-to-use online platform for the construction, customization, and dissemination of open educational resources (OER) to reduce the burdens of unreasonable textbook costs to our students and society.

This is a curated list of free courses from reputable universities like MIT, Stanford, and Princeton that satisfy the same requirements as an undergraduate Computer Science degree, minus general education.

A free, independent, and open source set of curricula for learning languages.

This company sells conductive fabrics, woven not out of fiber but very, very fine wires. They seem ideal for sourcing primary components for building shielding - say, you're constructing an RF testing facility and you want to minimize leakage (or intrusive external signals). Or you're building yourself a Faraday cage for some reason.

Send them a graphic of some kind and they'll do custom fabric of it for you. No minimum order, they even sell test swatches.