BeNJ-GoS's Journal: Linux: Boot \ Shutdown using only SysRq keys. (Cool :) )

Taken from some comment i found on Slashdot, don't remember by who.
(keys are for i386 and PC hardware)

Alt-SysRq-r : Sets keyboard mode to xlate

Alt-SysRq-s : Sync all filesystems
Alt-SysRq-e : Term to all processes (except init)
Alt-SysRq-i : Kill to all processes (except init)
Alt-SysRq-u : Remount all drives read-only
Alt-SysRq-b : Reboot!

Often if the system was fubar it comes back when you get to the kill step, and pressing Alt-SysRq-r again puts the keyboard back in raw mode and you can get back to a console to start things back up.