A few great sites for learning new skills that I plan on incorporating in my web design work:
http://csstricks.com - most interesting part is the snippets section - they not only cover css but also PHP snippets of code.
http://www.smashingmagazine.com/2007/01/19/53-css-techniques-you-couldnt-live-without/ has a number of really great css rules.
https://ia.net/blog/100e2r/ A standard for making websites easy to read. As I get older, I'm increasingly irritated by text seeming to get smaller and smaller. This lays out some pretty good arguments for a more easily to use web.