Flexibility from distributed energy resources presents an enormous potential to provide various services to the smart grid. In this paper, we propose a unified hierarchical framework for aggregation and coordination of various flexible loads, such as commercial building Heating, Ventilation, and Air-Conditioning (HVAC) systems, Thermostatically Controlled Loads (TCLs), Distributed Energy Storages (DESs), residential Pool Pumps (PPs), and Electric Vehicles (EVs). Moreover, a multi-stage Nash-bargaining-based control strategy is proposed to coordinate different aggregations of flexible loads for demand response. Case studies are provided to demonstrate the efficacy of our proposed framework and coordination strategy in managing peak power demand in a community.