This document discusses the use of cloud computing for library services. It notes that within five years, all library collections, systems, and services will be driven into the cloud. It defines cloud computing and related concepts like web services and APIs. It explores how libraries can use the cloud for collaboration, mobility, services, and resource sharing. It contrasts the opportunities of scalability and lower costs with the challenges of security, connectivity and contingency planning. Trends include continued open source adoption and importance of data as a service. Tips are provided for both beginners and experts to experiment with cloud services.