Within the context of mounting pressures on existing resources and the environment, fuel cell systems can and probably will play a major role. From a second law standpoint, their potential for effectively contributing to solutions, which deal with these pressures is great. This is true for fuel cells as standalone systems and even more so as systems working in concert with more conventional energy conversion processes. In order to put these systems in perspective, a brief summary of existing processes for energy conversion is presented as are projections for future improvements. The principal types of fuel cell systems are then discussed. This is followed by a brief discussion of their second law role followed by some perspectives on the modeling and analysis needs for future fuel cell system developments.