If you do development on Macs and you don’t use MacPorts, you should seriously consider it, especially if you come from a Unix background. Formerly known as DarwinPorts, it’s the equivalent of the Debian package-management system for Macs, and exceedingly useful when you find you just need to grab a copy of libpng, or try something with PHP 5, or some such.
The documentation will help you get started, but it’s very handy when someone like Garrett Albright writes a helpful tutorial to explain some of the more obscure features. Thanks, Garrett!
You may also want to consider pkgsrc. If you work with more than one or two platforms having a unified software package framework across all of them is quite a time saver. Along with the common platforms a few obscure ones are supported as well. I’ve been using pkgsrc with Mac OS X for a number of years now with great success.
Not to play down MacPorts at all, though. It is quite a nice system indeed.