This paper considers the cooperative control of multiple nonholonomic systems. Time-varying cooperative control laws are proposed with the aid of the results of the graph theory. The proposed control laws are decentralized and make the states of the group of systems converge to a moving point. By suitable control variables, the proposed control laws can make the state of each system converge to a small neighborhood of the origin. Robustness of the proposed control laws to communication delays is also considered. As an application of the proposed results, formation control of wheeled mobile robots is discussed. The simulation results show effectiveness of the proposed results.