Sensing and monitoring of our natural environment are important for sustainability. As sensor systems grow to a large scale, it will become infeasible to place all sensors under centralized control. We investigate community sensing, where sensors are controlled by self-interested agents that report their measurements to a center. The center can control the agents only through incentives that motivate them to provide the most accurate and useful reports. We consider different game-theoretic mechanisms that provide such incentives and analyze their properties. As an example, we consider an application of community sensing for monitoring air pollution.