I haven't had a kernel panic recently, but if I remember correctly, I used one or both of these options:
Reboot holding Command + S to start in Single User Mode Type "/sbin/fsck -fy" without "", then hit Return Once your drive is checked, type "reboot" without "", then hit Return
Reboot holding Command + Option + O = F to start in Open Firmware Mode Type "reset-nvram" without "", then hit Return Type "reset-all" without "", then hit Return