This is an extensive list of useful cheatsheets covering everything from firefox to XML to AJAX to wordpress. Definitely something you can look through and nab some nifty information. Courtesy of Smashing Magazine.

Actionscript


Ajax


Apache


ASCII Character Codes


ASP


C# and VB.NET


CSS


CVS


C++


Django


Firefox


Google


HTML/XHTML


Java


JavaScript


Microformats


Misc


MySQL


Oracle


Perl


Photoshop/Gimp


PHP


Python


Regular Expressions


Ruby


Unix/Linux


Weblog


Windows


XML