Via Jean-Philippe Paradis, I came across this CSS tutorial by Xah Lee. It's nice because the page shows several examples of CSS effects. When you click on an effect, it takes you to a short tutorial that discusses the effect and shows the code. The tutorials also have links to other documentation.
If you're an expert CSS user, this probably won't be as useful to you as it is to someone like me who only rarely writes CSS. I always have to look things up and before seeing this page wouldn't have had any idea how to produce the effects or even how to find out efficiently.
If you don't already know this stuff and sometimes produce Web pages—even if it's with something like Org Mode—you should take a look at the page. I've bookmarked it in my Docs bookmark so I can find it easily the next time I need it.