In 2008, the first of three DAAD PhD-Summer Academies on human-machine Interaction in networked systems and multimodal interfaces was hosted at the University of Chile in Santiago de Chile. It is focused on three topics: Multimodal Human-Machine Interaction in Different Application Scenarios Modeling Human-Machine Interaction Social Networks, Trust, and Reputation Gesture-Based Interaction Interface and Interaction Redesign Computer Supported Collaborative Work Modeling Mobile Groupware Systems Evaluation Methods Learning Paradigms Optical Communication Systems This book summarizes the lectures presented at the Summer Academy, making the material available to interested academics and students.