Nebula is a Cloud Computing pilot under development at NASA Ames Research Center. It integrates a set of open-source components into a seamless, self-service platform, providing high-capacity computing, storage and network connectivity using a virtualized, scalable approach to achieve cost and energy efficiencies. The fully-integrated nature of the Nebula components provide for extremely rapid development of policy-compliant and secure web applications, fosters and encourages code reuse, and improves the coherence and cohesiveness of NASA's collaborative web applications. When completed, Nebula will offer cost-effective Infrastructure-as-a-Service(IaaS), Platform-as-a-Service(PaaS) and Software-as-a-Service(SaaS). As a hybrid cloud, Nebula enhances NASA’s ability to collaborate with external researchers by providing consistent tool sets and high-speed data connections.