A free archive of US Army field manuals for the downloading.
A free, online book on the C programming language. There is also a downloadable .pdf file of the contents of the e-book so you don't have to try to archive the whole website.
A technical guide released by the Electronic Frontier Foundation about detecting packet spoofing and injection on the part of ISPs for various purposes, among them preventing you from using the service that you're paying good money for.
An in-depth text on basic and advanced firewall construction using OpenBSD. A must-read for anyone seriously interested in security or networking!
An excellent tutorial on hardening CenOS Linux (and by extension Redhat Advanced Server).
How to construct your own brick oven from scratch. Granted, you'll have to put it in the back yard and it looks like a bunker. Heavily illustrated.
A wiki about international travel by international travelers. Talks about many different destinations, specific places and times you might want to visit, airports, local travel, things to do, food, telecommunications, and safety.
A fan-made guide to the sprawling webcomic that is Homestuck, broken down by acts and parts.
A blog post from the docker development team that talks about bestpractices for container security. Links to both CISbenchmarks and their own intro guide.
A service with a CC-licensed API (https://www.cryptocompare.com/api/)
that seems to be a one-stop shop for all things cryptocurrency. They have forums, an interactive comparison list, guides for many things, reviews of hardware, software, and services.
A wiki of ways to fix things, including teardowns, where, to get parts, video tutorials, and diagnostic procedures.