I've found a 100% repeatable way to panic the kernel under at least the i386 port.
   I discovered this by accident last night by mistyping, but it have been able to
   reproduce it under the GENERIC kernel with nothing wierd going.

   Typing:
	   mount <directory> <directory>
   where both instances of <directory> are the same filename causes a panic
   with the error message 'panic: locking against myself'.  Is this a known
   bug, and has it been addressed in -current?

Yes, this is known.  It has not been fixed yet.