EMAMP is a project under development that allows you to install apache, mysql and php on your mac for development use without altering system files. The advantages it has over other solutions are as follows:

• EMAMP management interface is isolated from the php/mysql/apache install used in development so if you break any of them you can still administer EMAMP.
• EMAMP is modular, you can add/remove modules at will, there is no minimum module requirements, say you only want to install apache then you can do that, if you only want to install mysql and access it via the EMAMP management using phpmyadmin or via the command line then you can without needing to install apache.
• EMAMP allows for concurrent modules of the same program, i.e. you can run php 5.2.9 and php 5.2.1 or whatever versions you like. The same applies to apache and MySQL.
• EMAMP uses edge modules, when a new version of php mysql etc is released a new EMAMP module will be compiled and released, old modules will still be available.
• EMAMP also has support for SQLite and PostgreSQL databases
• EMAMP uses a web interface run on a lighttpd server with a separate php installation from the web interface you can view your modules, download and install new ones, delete old ones, edit httpd.conf access mysql via phpmyadmin.

You can download EMAMP from source forge here

You can view Documentation for EMAMP here

Easy Mac Apache PHP MySQL is released under the Academic Free License 3.0