Previously, I’d found WAMP a pretty nice setup. Well, there’s a comparable installation for Mac, as well. It offers a “Pro” version that gives you more flexibility as far as managing several virtual servers but the free version is pretty good for my needs.
From MAMP: Mac – Apache – MySQL – PHP:

The abbreviation MAMP stands for: Macintosh, Apache, Mysql and PHP. With just a few mouse-clicks, you can install Apache, PHP and MySQL for Mac OS X!
MAMP installs a local server environment in a matter of seconds on your Mac OS X computer, be it PowerBook or iMac. Like similar packages from the Windows- and Linux-world, MAMP comes free of charge.”