Ubiquitous user modeling differs from generic user modeling by three additional concepts: ongoing modeling, ongoing sharing, and ongoing exploitation. Systems that share their user models will improve the coverage, the level of detail, and the reliability of the integrated user models and thus allow better functions of adaptation. Ubiquitous user modeling implies new challenges of interchangeability, scalability, scrutability, and privacy. This volume presents results of a series of workshops on the topic of Ubiquitous User Modeling since 2003 and additional workshops at various other conferences e.g. on User Modeling and Adaptive Hypermedia in the last four years. The 8 revised full papers presented were carefully reviewed and selected from the best lectures given at the workshops and were significantly extended to be included in the book.