Direct hydrogen fuel cell power system as an alternative of current batteries is promising for portable applications because of its potential better energy and power density. Straight feeding hydrogen, which is generated from a chemical reaction process, to a fuel cell system requires a load-response hydrogen generation rate which is generally not easy to obtain. Hydrogen generation from the reaction between aluminum and water offers a simple way to acquire hydrogen which can be directly fed to a fuel cell power system, however, the oxide film formed on the surface of aluminum particles will generally stop the reaction to proceed. In the present review, metal aluminum activated by various techniques, namely by the addition of alkaline solutions, carbon materials, oxides and by alloying with other elements, are summarized. The effects of the additives on the hydrogen generation characteristics are evaluated. The available hydrogen generators based on the reaction between aluminum and water are discussed and some recommendations for future work are also proposed.