Mega list of free security learning resources

A living list — reply with your favorites and I'll keep it updated:

Web: PortSwigger Academy, OWASP Top 10, HackTricks.
Labs: TryHackMe, Hack The Box, OverTheWire, PentesterLab.
Reversing: Ghidra docs, crackmes.one, Nightmare (pwn).
CTF: picoCTF, CTFtime (upcoming events).
Blue team: Blue Team Labs Online, LetsDefend.
YouTube: LiveOverflow, John Hammond, IppSec.

What's missing?