If you don't want to bother setting your stylesheet up from scratch, you can find a good number of them ready made.
But a far better approach is to take a simple framework - such as header and footer with 3 columns - and customize it to meet your own requirements. It's a good way to learn, and again, there are plenty of these framework type layouts readily available.
BlueRobot An excellent jumping off point for those looking for simple framework stylesheets just asking to be customized.
CSSDrive Another selection of fundemantal framework stylesheets which you can tweak to suit your own needs.
CSSTinderbox There's a CSS related blog here (which is well worth reading) as well as a number of template layouts.
FreeCSSTemplates Just what you'd expect. Except it's quality content, not just a thrown together list of rehashed rubbish.
Glish An invaluable resource for those who are familiar with using tables to layout their site, but want to join the rest of us in the twenty-first century and use CSS instead.
SSIDeveloper A clear and concise selection of layouts.