Ivan, over at Creative Bits has put together an awesome tutorial about setting up a web server on your local Mac for testing dynamic sites.
From the site… “This is a beginner step by step tutorial that will help you set up your Mac, so that you can run PHP and MySQL locally and test the functionality of your websites. This post is written to graphic designers, who know little about programming, but are learning to incorporate PHP engines with MySQL databases into their web sites and want to test their designs in action or want to extend their services to include basic PHP functionality.”