Absolutely! ;3

W3 Schools is the best HTML/CSS site out there, but it doesn't account for HTML 5 or CSS 3.
CSS3.info is good for some of the newer css tidbits.
CSS Tricks has some neat CSS/HTML/PHP/JQuery/htaccess tricks
Other than that, I learned by reading code of other template makers. ;3

Hey, Tequila, I was just wondering, since you seem to know plenty of good resources, if you know a good place offering tutorials on creating a CSS/HTML layout from scratch? I figured it's about time I learn how to make my own themes XD