Joe Block has made his packaging tool for OS X -- The Luggage -- available.
Packagemaker.app makes it nearly impossible to have someone review the changes you've made in a package. They have to rummage through screen after screen, trying to remember the previous settings. At Google, I wrote an internal tool using Make that allowed the other members of my group to easily review package changes - every package is generated by a Makefile, and since Makefiles are text, the diffs are easily presented by code review tools. We made a lot of packages for use with puppet and InstaDMG using that tool, and after I left Google, I wanted to have a similar tool available, so I wrote the Luggage.