It looks like there will be a third player in the Macintosh OS X Unix tool installation game soon. Gentoo (open-source creators of Gentoo Linux) is bringing their Portage software configuration and installation platform to OS X.
Fink, a long time player in the OSX unix tool installation game, is considered the current "leader", although there are some peculiarities in the way that it works, and to my mind, they install a bit too much GNU for my tastes... but then, I'm a FreeBSD kind of guy, not a Linux kind of guy anyway. In particular, I'm not enamored of the /sw directory that it likes to install stuff into.
DarwinPorts is from the FrereBSD side of the family, and is a little more to my liking, but they have not been moving as aggressively as the folks at Fink and thus only have a little under 300 programs available. Plus, they haven't done an update since February, which makes me a bit concerned for the long- term prospects. Installs are generally done in /opt, which isn't that much happier than /sw, but it is a little better.
We'll have to see how things go with Gentoo, but their background seems to be mostly on the PowerPC side of Linux, and they have done things like making bootable Linux CD's for recent Macs, which is a very good sign. I'm interested in seeing what happens with this, so hopefully you'll hear more about it as more information (and more importantly software) is available.