HTML Cheat Sheet
- HTML/XTML in one page
- HTML5: The Evolution of Web Standards by James Sugrue
- (X)HTML Elements and Attributes
- Doctype Declarations (DTDs)
- XHTML Character Entity Reference
- GoSquared HTML Help Sheet
CSS Cheat Sheets
- CSS in one page
- CSS Properties and Values
- All CSS Properties Listed Alphabetically
- CSS Shorthand Guide
- GoSquared CSS Help Sheet
Adobe Flash Cheat Sheets
ASP Cheat Sheets
PHP Cheat Sheets
- PHP Basics Quick Reference Sheet
- PHP Cheat Sheet
- PHP Security Cheat Sheet
- PHP Variable and Array Tests
- GoSquared PHP Help Sheet
MySQL Cheat Sheets
JavaScript Cheat Sheets
jQuery Cheat Sheets
- jQuery Cheatsheet
- jQuery 1.3 Visual Cheat Sheet by Antonio Lupetti
- jQuery Selectors by Bear Bibeault & Yehuda Katz
Unicode Cheat Sheets
XML Cheat Sheets
mod_rewrite and .htaccess Cheat Sheets
Resource by: http://collegegfx.com/all-the-cheat-sheets-that-a-web-developer-needs/