Links from around the internet that I have found useful or otherwise worthy of showing off here.

http://ai/
Did you know a domain name can just be a TLD? Now you do.
http://bitsavers.org/
Very useful digital archive of various computing and related documents.
https://colorforth.github.io/
Archive of Chuck Moore's site.
http://ctyme.com/rbrown.htm
List of various interrupts used on the IBM PC.
https://developer.mozilla.org/en-US/
Very useful reference for Web technology.
https://dlang.org/
Neat systems programming language, a better C of sorts.
https://ewontfix.com/
Blog by musl dev about how fucked up Linux is.
https://falstad.com/circuit/circuitjs.html
Interactive electronic circuit simulator.
https://www.felixcloutier.com/x86/
Quick reference for x86 instructions.
https://flatassembler.net/
The flat assembler, including flat assembler g which is my favorite assembler.
https://forth-standard.org/
The best programming language.
https://github.com/zedeus/nitter/wiki/Instances
List of instances for Nitter, an alternative JS-less frontend for Twitter.
http://www.greenarraychips.com/
Massively parallel FORTH chips.
http://homepage.cs.uiowa.edu/~dwjones/ternary/
Very useful information on ternary logic and such.
https://int10h.org/oldschool-pc-fonts/
Vector font versions of old-school PC fonts.
http://livescript.net/
Language compiling to JavaScript, ES6 support is lacking though.
https://llx.com/Neil/a2/index.html
Resource on the Apple ][ and 6502 in general.
https://millcomputing.com/
Mill architecture, neat VLIW architecture. Fairly vaporware though.
https://www.pastraiser.com/
Reverse-engineering info for old chips.
https://www.redblobgames.com/
Useful resource on gamedev techniques.
http://www.righto.com/
Useful and interesting blog about old computers.
https://www.sandpile.org/
Description of x86 data structures and opcode encoding.
https://sci-hub.se/
Any paper is open access if you try hard enough.
http://seasip.info/index.html
Info on CP/M and other old things.
https://sel4.systems/
Very cool microkernel.
http://vectrexmuseum.com/vectrexlinks.php
Vectrex!
https://vimm.net/
Nice resource to get old games.
http://visual6502.org/
Transistor-level simulation and information for the 6502 & other chips.
http://www.wtfpl.net/
Objectively best software license.