I went looking for a quick reference containing all of the known OS X startup, shutdown, and sleep command keys. I couldn't find one, so I put this together after a little research. Most of these are the same under OS 9 and earlier.
Startup Command Keys[Editor's note: Although many of these have been posted here before in various hints, I thought it might be worthwile to have them all in one article -- thanks to autohag for submitting the nice compilation. If there are any missing that you know of, add them as a comment and I'll revise the original article as necessary.]Close Open Windows - ShiftShutdown, Restart and Sleep Keys
Start from CD - C
Start from OS X - X (some machines)
Select Start Up Disk - Option
Reset PRAM - Cmd+Option+P+R
Start Up in Single User Mode - Cmd+S
Start Up in Verbose Mode - Cmd+V
Boot into Open Firmware - Cmd+Option+O+F
Eject CD at Startup - Hold down Mouse buttonDeep Sleep - Cmd+Option+Eject
Shutdown, Restart, Sleep Dialog - Control + Eject
Shutdown, Restart, Sleep Dialog - Power key on keyboard
Mac OS X Hints
http://hints.macworld.com/article.php?story=20011206110114612