MacBlog

Power On
Open Firmware
BootLoader
  BootX (/System/Library/CoreServices/BootX) is the default bootloader on Mac OS X.
    Load the Kernel
      kext cache (/usr/sbin/kextcache)
     /sbin/mach_init
       /sbin/init
         /etc/rc
           source /etc/rc.common
           /etc/rc.netboot (or rc.boot)
           kextd
           /usr/libexec/register_mach_bootstrap_servers /etc/mach_init.d
           launchctl load /Library/LaunchDaemons /System/Library/LaunchDaemons
           SystemStarter ${VerboseFlag}
           /etc/rc.local
           /usr/libexec/WaitingForLoginWindow

http://www.kernelthread.com/mac/osx/arch_startup.html