Is it just me or most developers like to implement functionality and logic for their websites and freak out when they have to make it pretty? I personally hate writing style sheets – CSS may sound easy, and I understand the concepts, but don't ask me to apply them. CSS Zen Garden is a demonstration of what can be achieved with CSS, and it's really impressive.
The strange thing is that CSS looks easy; but when I have to write them, the headache hits. I start to diligently work to make my pages pretty in one browser, I somewhat succeed and then try a different browser – total disaster.
Matthew Osborn, a colleague in the ASP.NET team, wrote some simple web sites with CSS lessons. Take a look at http://css101.osbornm.com/ and http://css201.osbornm.com/. He also recorded some webcasts: CSS 101: The Basics screen cast & CSS 210: Theory and Practice screen cast.
For a simple tip, if you need to test your website in multiple versions of Internet Explorer, you can use Multi IE to install them on the same machine.