smashing Magazine is one of the best site that i ever find in the internet. i just heard about this. It published several articles on different aspect of programming. You can easily increase your technical knowledge from this. This site always updated with latest article, tutorial etc. It includes article and tutorial on

CSS, AJAX, PHP, Web 2.0, Ruby, XML, DHTML, JS, framework and many more.

I get much help from this site and become a big fan of this site. I hope it will also works for you.