Rawsec's CyberSecurity Inventory
is an inventory of tools and resources about CyberSecurity that aims to help people to find everything related to CyberSecurity.
is a blog talking about Linux and security but also where Rawsec CTF team posts challenge write-ups.
is a lovely Ruby language cheatsheet.
The Hacking Trove
is the hacker technical cheat sheet and it can definitely help you during your penetration test, technical security audit, PWK/OSCP Lab or exam, CTF, challenge, training, etc. by providing cheat sheets, tools, examples, references, etc.