Use this online FavIcon Generator to easily create a favicon (favorites icon) for your site. A favicon is a small, 16x16 image that is shown inside the browser's location bar and bookmark menu when your site is called up. It is a good way to brand your site and increase it's prominence in your visitor's bookmark menu.
The Cascading Style Cheatsheet lists the most useful CSS properties with examples. Comes in very handy.
Dead Centre This is a very simple example of how to horizontally AND vertically center a block using CSS.
There are many ways to make a table look "pretty" using CSS. This HTML and CSS Table Border Style Wizard let's you click on different table elements and change their look/feel. The CSS is instantly updated to show you what you've come up with.
The same site also has a CSS Font and Text Style Wizard that does the same thing for text.