Google Project Zero - Zero day research from Google
https://please.dont-hack.me/books/hacking/
Must have cheatsheet, r/AskNetSec
http://null-byte.wonderhowto.com/how-to/
http://www.offensive-security.com/metasploit-unleashed
http://resources.infosecinstitute.com/
http://www.windowsecurity.com/articles-tutorials/
http://www.sans.org/reading-room/
http://packetstormsecurity.com/files/
https://www.corelan.be/index.php/articles/
http://opensecuritytraining.info/Training.html
https://www.blackhat.com/html/archives.html
http://magazine.hitb.org/hitb-magazine.html
https://www.hacksplaining.com/lessons
https://cybersecuritybase.mooc.fi/
https://packetstormsecurity.com/
James Mickens - Harvard cybersecurity professor
10 Cybersecurity Podcasts, r/cybersecurity
23 Practice sites, r/HowToHack
http://overthewire.org/wargames/
https://exploit-exercises.com/
https://ctf.hacker101.com/about
Security Programming Projects, r/AskNetSec
http://sourceforge.net/projects/metasploitable/
http://ophcrack.sourceforge.net/
https://n0where.net/blackarch-linux/
http://sourceforge.net/p/attackvector/wiki/Home/(edited)
Vulnerable sites, software and wargames
https://cybr.club/Important-Links/
https://www.hacksplaining.com/
https://www.exploit-db.com/google-hacking-database - Making it easier to use Google queries for pentesting