is this a cinder block? I would first try to find out why the foundation is shifting and what more is going to happen with this crack. This does mean that something is happpening with water or earth settling. Is water draining away from your home on all sides?
I have had great luck with patching concrete that is under stress or does move slightly. Its a latex concrete patch. The latex will allow some movement before it cracks again. Comes in a box dry located in the building material sections of home centers. Check it out.