Cloud computing has seen a surge in recent past, and is widely used by organizations to meet their daily computational needs. However, the drawback of the large scale adaptation is the massive energy demands of the cloud service providers to ensure round the clock availability of the service. A cloud based data center may require as much energy as that of 25,000 households. Studies suggests that by using energy efficient techniques, cloud service providers can save as much as 80% of the energy. In this work, we present future research directions for energy efficient data centers using virtual machine migration. We focus on single host and multiple host virtual machine migration and consolidation to reduce the total energy consumption. Keywords: Cloud Computing, Energy Efficient Algorithms, Green Cloud Computing, Virtual Machine Migration.