Misc.

Staging area for categories without homes

Links to links

Ooh Directory Blogs
Everything Moe Weeb shit
Free Media Heck Yeah
Ripped
Tiny Tools Simple tools, aimed at people making indie games & similar
Webring List
The Index Weeb shit
Curlie Old school link directory
Cloudhiker Modern successor to Stumbleupon
Black Stump Old school link directory
Indie Web Directories Directory of directories (which might in turn link to directories themselves...)
Open Image Collections
Indieseek Directory of indie sites
Bukmark Club Directory of sites like this sub site
Blogroll.org Blogs
Creative Commons Hub Directory of places to find things that are likely to be licensed CC
Linklane Web listing
Blogroll Club More blogs!
Blogs.hn Tech blogs
Kagi Smallweb Another stumbleupon-like
Divergent Rays's Linkware Archive Properly sourced retro web graphics
Anilinks weeb shit, doesn't seem updated
Smooth Sailing
Environment Web Directory As implied by the name, focused on the environment
Awesome Piracy
A Website is a Room
Forum Directory
Piracy Index
Awesome Lists List of Github 'Awesome lists'
Sozai Directory List of JP sites offering pre-made layouts/graphics/etc. Very stylish, has examples of what each site's resources look like
Art Resources Database
Resource List for the Personal Web Collection of resources for creating and maintaining a website
Annotated Subject Directory for the Web Well organized general directory
URL Town

Compsci Edutainment

War games, puzzle games that require you to write code to solve them, etc.

NAND Game Circuit boards
Deadlock Empire
SQL Noir
Select Pink CSS
CMD Challenge
Over the Wire
Project Euler Mathematical problems that require programming to solve. Has a sort of Advent of Code vibe almost?
Advent of Code Speaking of which. While it's in advent calendar format, you can work on old problems freely any day of the year
Pwnable.kr
Hack This Site
0x0539
IO
Pwnable.tw
Smash the Stack
3564020356
XSS Game
Vulnhub
Hacker Test
Network Forensics Puzzle Contest
W3 Challs
CTF Time
Microcorruption
Ring Zer0 CTF
Untrusted Javascript
Flexbox Froggy CSS Flexbox

Online Courses

Red Cross
Harvard
Alison
Stanford
MIT OpenCourseWare