The potential of emerging technologies such as fuel cells (FCs) and photovoltaics for environmentally-benign power generation and conversion has sparked intense interest in the development of new materials for high density energy storage. For applications in the transportation sector, the demands placed upon energy storage media are especially stringent, as a potential replacement for internal combustion engines — the PEM FC — requires hydrogen as a fuel. Although hydrogen has about three times the energy density of gasoline by weight, its volumetric energy density (even at 700 bar) is roughly a factor of six smaller. Consequently, the safe and efficient storage of hydrogen has been identified as one of the key challenges to realizing a transition to FC vehicles. This talk will present an overview of our recent efforts aimed at developing new materials for reversible, solid state hydrogen storage. A tight coupling between first-principles modeling and experiments has greatly accelerated our efforts, and several examples illustrating the benefits of this approach will be presented.