RACHEL - Remote Area Community Hotspot for Education and Learning. An opensource project for a raspi that serves an offline libary of educational material for bandwidth poor locations. education Includes what they call "utility content," which seems to be reference material. OER - Open Educational Resources. Internationalized. software archive

Peter Gutmann has put what he calls his Godzilla Crypto Tutorial online for everyone who wants it to download and learn from. It's 973 slides across twelve chapters and is fairly high level in scope - it won't teach you about AES, but it will talk about cryptographic protocols as a whole. If you're interested in crypto, this would be a good resource for teaching yourself.