Pudge has been posting recently about nifty stuff you can do with the Mac::Glue Perl module. Must investigate further, automation is fun.
In particular he's taken care of a problem I referenced earlier wrt SSH agent environment variables not being populated when you startup the native (or sorta native) distribution of emacs. His automation creates an SSH agent at startup and fills up the ~/.MacOSX/environment.plist file with the relevant information. Emacs can read this just like a shell initialization file (e.g., ~/.bashrc). Cool.