In Mac OS/X Tiger, Apple introduced a new type of system
startup called launchd, which replaces many tasks traditionally run by
either process number 1 (init) or cron. launchd is controlled by
property files (XML) which can be daunting to write. Enter Lingon, a free
tool by Peter Borg which allows to easily create new and modify existing
launchd property files.
An indispensable tool for anybody who wants
to tweak launchd.