With increasing numbers of energy hungry data centers, energy conservation has now become a major design constraint for current and future Infrastructure-as-a-Service (IaaS) cloud providers. In order to efficiently manage such large-scale environments three important properties have to be fulfilled by the management frameworks: (1) scalability, (2) fault-tolerance and (3) energy-awareness. However, the scalability and fault tolerance capabilities of existing open-source IaaS cloud management frameworks are limited. Moreover, they are far from being energy-aware. This chapter first surveys existing efforts on building IaaS platforms. This includes both, system architectures and energy-aware virtual machine (VM) placement algorithms. Afterwards, it describes the architecture and implementation of a novel scalable, fault-tolerant and energy-aware VM manager called Snooze. Finally, a nature-inspired energy-aware VM placement approach based on the Ant Colony Optimization is introduced.