The SANS Institute provides some of the best security training in the industry. Many of their classes include the so called “Cheat Sheets” which are short documents packed with useful commands and information for a specific topic. I have linked as many as I am aware of below.
Most of these will require a login to the SANS website. Accounts are free.
Intrusion Discovery Cheat Sheet for Windows
Intrusion Discovery Cheat Sheet for Linux
Windows Command Line Cheat Sheet
Misc Pen Test Tools Cheat Sheet
Linux Intrusion Discovery Cheat Sheet
Windows Intrusion Discovery Cheat Sheet
Forensics Cheat Sheet and Catalog
Google Hacking and Defense Cheat Sheet