hackthebox.com	One of the best platforms to hone your hacking skills.
tryhackme.com	Great up-to-date learning platform. Especially if you are starting on your journey.
PortSwigger Academy	This is an absolutely excellent material for web application hackers.
cryptohack.org	Probably the best platform to get into cryptography hacking.
linuxjourney.com	Great resource to learn linux and get comfortable with it.
ctftime.org	Prime resource for finding CTF hacking competitions and registering there.

Some additional resources of more varying quality…

BugCrowd University	Very nice articles and reading materials.
Intigriti Hackademy	Quite lightweight and nice articles for main vulnerability categories.
pentesterlab.com	One of the best known hacking platforms, lot of more advanced topics. Monthly subscription.
cyberseclabs.co.uk	Good platform to learn network hacking. Access to all labs costs about 10-15$/month.
ctf.hacker101.com	Now this one is a ctf program with accompanying training from HackerOne – the bug bounty platform. Their training is mostly video materials, a bit on the boring side, but CTF can be good and has rewards (get invited to private programs).
play.picoctf.org/practice	Some good CTF challenges.
hackingloops.com	Nice articles, good reading materials.
Crackmes.one	Ton of binaries users can upload and reverse engineer/hack. Be careful not to run into malware.

Nice sites that catalogue and resource other pen-testing sources.

github.com/Muhammd/Awesome-Pentest	Great collection of Pentesting recources
www.redteamtrainingreviews.com	Awesome listing on Red-Teaming trainings/platforms
github.com/swisskyrepo/PayloadsAllTheThings	A list of quite useful payloads for Web Application Security