Networking & Cyber Security

David Bombal: David Bombal provides a variety of training materials CCNA exam preparation, Network Automation, Python, Linux, SDN… and more.
Network Chuck – Hack Your Career: Whether you want to become a network engineer, a hacker, cloud engineer or just want to know how to get started in IT…
Vicki Li: Vickie Li’s Security Blog.
Portswigger: PortSwigger offers tools for web application security, testing, & scanning.
We Hack Purple: Secure All The Things!
OWASP Top 10

SQL

OWASP – SQL Injection
OWASP – SQL Prevention Cheat Sheet
PentestMonkey
Rhana Khalil’s Video Slides
The Web Application Hacker’s Handbook: Chapter 9 Attacking Data Stores