Cheatsheet (CS) is a / several page(s) of condensed information on certain topic, which acts as a quick reference. It’s very handy because it’s just a page with most of the information that you need already there. Remember your cheatsheets back then when you’re still at school ? Amazing isn’t how much information we all managed to cram on so little piece of paper 🙂
It’s basically the same, but these cheatsheet are not for school exams – they’re for life exams : our daily job.

Note that creating a good cheatsheet is no easy task. Some authors have donation links put up on their pages. Therefore, if you found anything useful (eg: saved you lots of time / it’s a lot of convenience / actually saved your butt), consider donating. The authors deserves it.

Here I’ll try to list all (good quality) cheatsheets on IT. If you see something missing, please feel free to comment, and I’ll add it. Thanks.

1. ActionScript
   • ActionScript 2.0 CS
   • Thotskee ActionScript 3.0 flash.display Package CS
   • Thotskee ActionScript 3.0 Packages CS
   • Thotskee ActionScript 3.0 Top Level Classes CS
2. Apache : As the swiss-army knife of webserver, Apache is indeed very flexible, and has a lot of configuration settings. The result: even seasoned Apache admins will be forced to dig their Apache bibles from time to time to be able to do certain things. The cheatsheets below aim to help them with that.
   • Pete’s Apache CS : basic Apache CS, useful with daily tasks. Not very comprehensive, but should be enough for most.
   • Andrew’s Apache 1.3.x CS : Quite comprehensive, probably the best Apache 1.3.x CS out there.
   • Dave’s mod_rewrite CS : This is one of the most powerful of Apache’s modules. Beginner Apache admins tend to avoid this plugin whenever they can. Some breathes this daily though. All should be able to benefit from this cheatsheet.
   • Jackol’s htaccess CS : nice one !
3. ASCII codes
   • ASCIItable.com : After I lost my ASCII ref. card from PC Computing magazine, I found this website. Good stuff.
   • Unicode v4 CS : also from asciitable.com
   • VisiBone’s complete Unicode CS : 65,000+ of them !
4. ASP : To be honest, I’m no ASP expert. So your suggestions are especially welcome on this.
   • Dave’s ASP & VBscript CS
5. Blogs
   • Wibbel’s Blogger.com CS
   • Wibbel’s WordPress CS
   • WordPress Plugin API CS
   • Ollieman’s Markdown CS
   • A MoveableType CS : I don’t really know what it says on the page, but if you scroll down a bit, there’ll be a download link fo the English version of the MT’s CS.
6. C & C++(aka THE programming language)
   • Joseph’s C cheatsheet
7. CSS (Cascading Syle Sheet) :
   • Dave’s CSS CS : This one’s a true cheatsheet – only a page long, and crammed quite a lot of info in it.
   • Jung’s CSS1 CS
   • Jung’s CSS2 CS
   • Roger’s excellent CSS shorthand CS : a real eye-opener for many.
8. Database
   • Basic MySQL CS
   • Dave’s MySQL CS : Pretty good.
   • Pete’s PostgreSQL CS
9. Debuggers
   • Andrew’s GDB CS : It’s quite old, but some may still find it useful.
10. Editors
    • VI CS : the one I’m using 🙂
    • Lagmonster’s VI CS :Quite long, but easy to understand for novice.
    • Lagmonster’s Advanced VI CS
    • Andrew’s emacs CS
    • Laurent’s VIM CS
    • Joseph’s TeX CS : well, it’s not exactly an editor, but there you go (I think I’ll separate this into it’s own section)
11. HTML (Hyper Text Mark-up Language) / Web in general :
    • Webmonkey’s HTML CS : Oldies, but goodies.
    • VisiBone’s HTML CS : probably the most comprehensive out there
    • Webmonkey’s Color Codes CS : A bit long, but it’s organized a bit differently than Dave’s, and some may prefer this.
    • Dave’s Color Codes CS : Just a page, and should suffice for most
    • LogoOrange.com’s Color Code CS : CMY, RGB, and Pantone !
    • Dave’s HTML Character Entities CS
    • Jung’s HTML DOM CS
    • Jung’s XHTML 1.0 frameset CS
    • Jung’s XHTML 1.0 transitional CS
    • Jung’s XPath CS
    • Jung’s XLS CS
    • Jung’s XSLT CS
    • UMBC’s Semantic Web CS
12. Java
    • Peterson’s JSP 2.0 / JSTL CS
13. Javascript :
    • Webmonkey’s Javascript library : NOT a cheatsheet, but Webmonkey’s contents are of very high quality and useful; and many may find this useful. Check it out.
    • Dave’s Javascript CS : Quite complete, just 1 page.
    • VisiBone’s Javascript CS : as usual, very comprehensive.
    • VisiBone’s Javascript Regex CS : VisiBone seems to be a producer of high-quality products. Impressive.
14. Microformat : frankly, the first time I heard about Microformat is when I browsed Dave’s excellent website. Looks very interesting.
    • Dave’s Microformat CS
    • Labnotes.org’s Microformat CS
15. Perl :
    • The Perl CS : Most will find no reason to look for something else.
    • Catalyst CS : it’s a web application framework for Perl
16. PHP :
    • Dave’s PHP CS : Not bad, but for something as extensive as PHP, the cheatsheet may need to be more than 1 page long.
17. Regex (Regular Expressions) : You’re not a true programmer if you have no idea what Regex is. For those wishing to learn it, many found Regex Coach to be a great help.
    • Dave’s Regex CS
18. Ruby on Rails :
    • Dave’s RoR CS
    • glu.ttono.us’ Configuring RoR CS
19. Security : somebody actually had the idea to make CS for this ! well done.
    • XSS CS : from the folks @ ha.ckers.org
    • Web Application Testing cheatsheet
    • SQL Injection cheatsheet : very, very comprehensive. A book material me think.
20. UNIX
    • Marc’s UNIX CS : warning, very old ! last updated on 1996. However, it’s really (REALLY) amazing that it’s still up after 10 years. So here it is, as an honour to the author (and maintainer).
    • The One Page Linux Manual : another classic, and still very useful.
    • Linux Admin CS
    • Pixelbeat’s Linux CS : quite thorough.
    • Bash scripting CS
    • Linux Directory Structure CS
21. Utilities : there are numerous utilities out there. Some are very useful, yet rather hard to use (to put it politely). Here are a few CS to help you with it
    • Screen CS : screen is a small UNIX utility which is very useful for remote work – if your connection got disconnected, just reconnect again, and your terminal will be as before you got disconnected.
22. Version Controls
    • Andrew’s CVS CS
    • Laurent’s CVS CS
    • SVN cheatsheet
23. Web Services
    • About.com’s Google CS
    • About.com’s Yahoo CS
    • Evan William’s gmail CS
24. Miscellaneous : other bits still relevant to IT
    • VisiBone’s Country Codes CS
    • Laurent’s UML (Unified Modeling Language) CS
    • XUL Widget’s CS
    • Firefox CS
    • Anandtech’s CPU CS : is this really a cheatsheet ? I don’t care really, I just like the idea !

More links : del.icio.us’ cheatsheet tag.