Online Cheatsheets

http://overapi.com  

• Python, Regex, Linux, Mysql, Ruby, JS, and many more (A-Z choice)

https://lecoupa.github.io/awesome-cheatsheets/

• Docker, Kubernetes, Redis, React, Angular, Django, Bash, PHP, C, C#, Javascript

https://www.sans.org/blog/the-ultimate-list-of-sans-cheat-sheets/

• SANS Cheatsheets - Various Subjects