There are a ton of free cheatsheets, quick references, and downloadable resources for programming languages and related technologies online — in this post I’ve tried to organize and list some of the best for web development.
As far as I can tell, all of the material assembled here is freely available. I’ve tried to avoid anything that points to pirated or illegal content. Please let me know if you see anything that isn’t supposed to be free and I’ll remove it from the list.
Please post suggested additions to this list as comments!
Meta-reference sites — organized lists of references and cheatsheets:
A wonderful online API reference covering many programming languages.
An organized list of quick references and cheatsheets.
A great site with links to cheatsheets on lots of programming languages.
Another great site organizing various cheatsheets.
A very long and thorough set of links to cheatsheets all over the web.
Other meta-reference sites:
Key providers of cheatsheets:
Visibone, the company that makes the best commercial cheatsheets for HTML, CSS, colors, etc. Site includes free resources and downloadable versions of several great cheatsheets.
Original cheatsheets for HTML, CSS, PHP, and other technologies.
Original cheatsheets for CSS, XML, and related technologies.
Free version of Visibone’s HTML cheatsheet.
HTML cheatsheet from Andrew Ford.
HTML cheatsheet from Ian Graham.
HTML cheatsheet from ILoveJackDaniels.
HTML cheatsheet from Liquidcity.
Maran Wilson’s HTML cheatsheet.
Florian Schmitz’s HTML cheatsheet.
An online reference to HTML organized by tag.
Brian Wilson’s online HTML reference.
ILoveJackDaniels’ HTML character entities cheatsheet.
CSS cheatsheet from DeepX.
CSS cheatsheet from Ian Graham.
CSS cheatsheet from ILoveJackDaniels. (And really, who doesn’t?)
CSS cheatsheet from Liquidcity.
CSS cheatsheet from Spectrum Research.
CSS cheatsheet from Veign.
CSS cheatsheet from Brett Merkey.
CSS cheatsheet from Leslie Franke.
CSS cheatsheet from Matt Robinson.
Online CSS reference from Brian Wilson.
CSS online references from Eric Meyer.
A detailed overview of CSS from 2006 that covers features that work on most browsers.
Browser compatibility matrices:
Visibone’s free interactive web color picker.
Visibone’s free web color quick reference guide.
Veign’s web color reference guide.
PHP cheatsheet from ILoveJackDaniels.
PHP 4 reference card from Steven Gould.
BONUS — Google cheatsheets:
Official Google cheatsheet.
Google advanced operators cheatsheet from Google Guide.
BONUS — free downloadable programming books:
Outstanding site organizing links to many free programming books, tutorials, and lecture notes.
Another organized set of links to free programming books.
Other sites for free programming books: