Here it is, by popular, frustrated demand: The master list of every secret (or not-so-secret) keystroke in Mac OS X Leopard, including all of the keys you can press during startup. Clip and post to your monitor (unless, of course, you got this book from the library).
For the most part, the following list doesn't include the keystrokes that are already listed in your menus, like -P for Print, -S for Save, and so on.
Keys to Hold Down
Starts up from a CD
Starts up from the first partition
Starts up from network server
Resets the laptop screen
Puts the Mac into FireWire Target Disk mode
Starts up in Mac OS X (if 9 is on the same disk)
Shows icons of all startup disks and partitions, so you can choose one for starting up.
Starts up from external drive (or CD)
Zaps the parameter RAM (PRAM). (Hold down until you hear the second chime.)
Brings up Open Firmware screen (pre-Intel ...