There are a few ways how to spice up your Mac with unixish Open Source software: Fink uses the Debian package manager and overall works pretty well, yet it seems as if it has been loosing momentum lately, many package versions date back quite a bit. A reason for this could be MacPorts (formerly know as Darwin Ports) which generally features more up-to-date package versions. Unfortunately, it's package manager falls short in many areas, most notably dependency handling.
Thus I'm rather unhappy with either of them, especially as our servers are running Gentoo Linux and I've soon come to love the power of it's package manager Portage. Why can't there be anything like that on Mac OS X?
Well, there is! The project is called Gentoo Prefix and aims at bootstrapping Gentoo Linux in any subdirectory you choose. The initial installation on Mac OS X takes more time, yet it's painless and you're rewarded with all the power of Gentoo and Portage running right on your Mac OS X Mach kernel. What a beauty!