Actually, _JT_'s code won't work because it's in the wrong order.
$().SPServices.SPCascadeDropdowns({ relationshipList: "Types", relationshipListParentColumn: "Departments", relationshipListChildColumn: "Title", parentColumn: "Department", childColumn: "Types", simpleChild: true });
You can switch to a simple child dropdown by adding the simpleChild option to the SPCascadeDropdowns call per the docs.
M.