The odcctools project is geared towards improving the Darwin cctools build system and code base to support Darwin development.
The mailing list archives and subscription page can be access at http://www.opendarwin.org/mailman/listinfo/odcctools
Darwin cctools has several components, including the assembler as(1), the static linker ld(1), various tools for manipulating and analyzing Mach-O and fat files, and support libraries. It is broken down by components here.
That latest odcctools snapshot can be downloaded from http://www.opendarwin.org/downloads/odcctools-20050327.tar.bz2. You can also access the CVS sources:
cvs -d :pserver:anonymous@anoncvs.opendarwin.org:/Volumes/src/cvs/od login cvs -d :pserver:anonymous@anoncvs.opendarwin.org:/Volumes/src/cvs/od co -P odcctools
You can use odcctools with mainline gcc from gcc.gnu.org. The "apple-local-200502-branch" has some Apple-specific changes and build tools - odcctools should work with either version. Instructions for using odcctools with gcc can be found here.