I've crossed with several design web sites. There's lot of them out there, but these I found particulary interesting.
One has an article with 50 lessons about graphy design theory. It's called 50 Totally Free Lessons in Graphic Design Theory and I've learned a lot from it. If you're looking for design information, this site will certainly be helpful.
Another one is a web site that collects web pages that suck. It's called Web Pages That Suck and it states that "it give us the opportunity to learn from other people's mistakes without having to make them ourselves". I agree. It's a good example of how not to design web pages.
Finally there is an article about basics of good web design. It's called 9 Essential Principles for Good Web Design and has useful information about how to do good web design.