Like w3schools

http://www.tutorialspoint.com/index.htm

Cheat Sheets for Front-end Web Developers

http://sixrevisions.com/resources/cheat_sheets_web_developer/

10 Ways to Improve Your Web Page Performance

http://sixrevisions.com/web-development/10-ways-to-improve-your-web-page-performance/

w3fools.com

Tutorials for HTML, javascript and CSS

Free Joomla Tutorials

http://www.freejoomlatutorials.com/

Ajax Tutorials

http://www.roseindia.net/ajax/ajax-tutorials.shtml

Tutorials for joomla, wordpress, php

http://www.opensourcevarsity.com/#wptutorials

ebooks
http://www.opensourcevarsity.com/ebooksdownload