As far as HTML/CSS:
This may not be what you're looking for, but I often Right-Click > View Source to see the output of sites I find interesting. In the head you'll see the path to their CSS, which you can generally paste into your address bar and open/save.
I like to see the different strategies people use to style their HTML, and this is the most direct means of doing that.
I learned a lot early on about elegance and economy, letting the cascade do the work for me, naming and formatting conventions, and so on, using this technique.
I won't list a bunch of sites for you because you can google them yourself and see what peaks your interest.
http://www.alistapart.com/ is a very good resource; you might start there.
Bear in mind that while the HTML5 and CSS3 specs are somewhat usable already, they are not complete. Good resources which deal specifically with the current specs will be just fine for learning/refreshing.
Don't get hung up on the technology - focus on semantics and structure, good practice and maintainability.