"Designing with Web Standards" covers HTML, CSS, and light JS, but importantly hammers home the concepts of progressive enhancement, graded browser support, and working around browser quirks in a sustainable manner
"CSS Mastery" is a foundational text, as far as I'm concerned, covering a combination of common techniques and as well as covering the browser rendering model brilliantly
On the JS Side, "DOM Scripting" was fantastically handy for me, as it covers the DOM event model, modifying the DOM in place, and the proper way of building sustainable scripts. I read the 2005 edition back when it was new, but there's a 2010 edition out now which may be worth looking into:
"Don't Make me Think" covers web usability and is a great jumping off point for further learning.