For Wikipedia: A cheat sheet or crib sheet is a concise set of notes used for quick reference. “Cheat sheet” may also be rendered “cheatsheet”.
People working in informatics in general and on unix terminals in particular know that is not so easy remember every single command and so it’s usual to have “Cheat Sheet”, a collection of the most useful commands in a single A4 page for a particular program or environment.
And this is my small collection.
General and Terminal Linux cheat sheets
Generic Bash – How variables can be assigned, and some general informations.
Linux Command Line Reference – A lot of commands that you can use from the command line, from ls to iproute 2 and sed commands.
Unix/Linux Command Cheat Sheet – Available in many languages
Programs, software cheat sheets
Graphical vi-vim Cheat Sheet and Tutorial – This is a single page describing the full vi/vim input model, the function of all keys, and all major features.
Emacs Cheat Sheet – If you prefer Emacs.
Mozilla Firefox Cheat Sheet 2005 edition, still very usable.
Mozilla Thunderbird Cheat Sheet 2005 edition, still very usable.
Cheat Sheet of programming languages
Perl refereferenc card Contents: variable types, basic syntax, references and data structures, system interaction, input/output, regular expressions, object-oriented perl and modules, and one-liners.
Python Cheat Sheet one-page reference sheet for the Python programming language.
Ubuntu 11.04 Natty Narwhal – Unity Cheat Sheet – If you really want to use Unity, this is for you.
KDE And Konquerer Keyboard Shortcuts from techrepublic, need registration.
Gnome shell, cheat sheet web page
Debian – Debian specific (based on Lenny)
Debian reference card in many languages.
Fedora – Fedora 14 cheat sheet
Opensuse – Opensuse Zypper and Osc cheat sheet.
Ubuntu reference card – 2008 Edition
http://bhami.com/rosetta.html – This is the Rosetta stone for *nix systems, if you work with AIX, Solaris or something else, this is a link you must check.
Not enough ?
Here you can find a compilation of approx 70 cheat sheets for Linux users.