Link: Rob Landley's Linux Memory Management Frequently Asked Questions
Rob Landley's Linux Memory Management Frequently Asked Questions is what it says in the title (via). As of writing this pointer to it, the current version of the FAQ appears to be from 2014, but much of its information is relatively timeless.
Landley's FAQ is good for a lot more than Linux specific information. It's a good general overview of a number of hardware MMU concepts and general Unix MMU concepts. Things like page tables, TLBs, and even memory mappings are basically universal, and the FAQ has a nice solid explanation of all of them and much more.
Link: Introduction to Certificate Transparency for Server Operators
Alex Gaynor's Introduction to Certificate Transparency for Server Operators (via) is what it says in the title, and taught me some things about certificate transparency in practice. Sadly, one of the things it taught me is that once again Lighttpd seems to be coming up short as far as modern TLS goes. I really should switch over my personal site to using Apache, even if it will kind of be a pain because Fedora fumbled good Apache configuration.
(I also hadn't known about Cert Spotter, which has the advantage that you don't need a Facebook login to use it and thus don't have to helpfully (for Facebook) tie one or more domains to your Facebook login. All you need is an email address and on the modern Internet, you already need a source of individualized disposable ones.)