Amongst a lot of other great stuff, MacOS X 10.3 ships with MySQL and Ruby. Ruby, for you die-hard php/perl fans out there, is a splendid object-orientated language that performs very well on the Mac, too. You can even integrate it in the Aqua environment by using Cocoa classes -- check out Ruby central and RubyCocoa.
Download the package at dev.mysql.com, unpack it and type the following in the folder where the install data resides.:Mac OS X Hints
http://hints.macworld.com/article.php?story=20040614173314772