jasonwood - The closest thing Mac OS X has to safe mode is to hold shift at start up which simply means the computer starts up only with Apple kernel extensions.
apple=god - Are you unable to log in? Or not even able to access single user mode (hold command-S at startup). If you're not familiar with using the command line in UNIX I suggest you avoid single user mode for now and try holding command-V and see where the process stalls.
Got Mac? - Everyone I've ever talked to refers to holding option to start up off another drive as a startup disk changing mode. Never a safe mode, as safe mode under OS X and Windows has always referred to a mode that should be able to boot in case the full "production" mode doesn't work. (eg. with 3rd party utilities and such running)