Examining a kernel crash dump with a graphical debugger like ddd is also possible (you will need to install the devel/ddd port in order to use the ddd debugger). Add the -k option to the ddd command line you would use normally. For example;

# ddd --debugger kgdb kernel.debug /var/crash/vmcore.0

You should then be able to go about looking at the crash dump using ddd's graphical interface.