A fluid flow induced oscillating energy harvester includes a stand supporting the harvester in a fluid flow; a support member mounted for movement relative to the stand in a direction perpendicular to the flow direction; a bluff body positioned substantially perpendicular to the flow direction and pivotally mounted to the support member at a position off-center from the center of mass of the bluff body, wherein sufficient fluid flow causes an oscillating movement of the bluff body and the support member relative to the stand; and an electrical generator coupled to the support member and configured to convert oscillating movement of the support member to electrical power. The harvester may include a support member spring supporting the support member for oscillation about a support member rest position wherein the support member spring exhibits a higher stiffness at higher oscillation amplitudes of the bluff body and the support member.