A quick reference guide for regular expressions (regex), including symbols, ranges, grouping, assertions and some sample patterns to get you started.
A cheat sheet of the commands I use most for Linux.
A quick reference guide for CSS, listing selector syntax, properties, units and other useful bits of information.
A guide to the parameters sent with all requests to Google Analytics via __utm.gif
A quick reference guide for PHP, with functions references, a regular expression syntax guide and a reference for PHP's date formating functions.
Tips for equalization. By frequency, by instrument with a glossary.
A cheat sheet for Wikipedia, including markup help.
A mod_rewrite Cheat Sheet - a quick reference guide for mod_rewrite, with rewrite flags, regular expression syntax and sample rules.
A list of Regular Expression functionality supported by Google Analytics