rlucia writes: "Now we have some patches to The FreeBSD Ports Collection to make it working on Darwin 1.3 (as shipped with Mac OS X). I also patched pkg_* from FreeBSD source tree to use with Darwin. The work is at early stage but I could compile and install (also deinstall) lots of packages."
Check it out at Darwin pkg, Darwin ports or compiled packages files.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20010403174637269