While the user-centered design methods we bring from human-computer interaction to ubicomp help sketch ideas and refine prototypes, few tools or techniques help explore divergent design concepts, reflect on their merits, and come to a new understanding of design opportunities and ways to address them. We present Speed Dating, a design method for rapidly exploring application concepts and their interactions and contextual dimensions without requiring any technology implementation. Situated between sketching and prototyping, Speed Dating structures comparison of concepts, helping identify and understand contextual risk factors and develop approaches to address them. We illustrate how to use Speed Dating by applying it to our research on the smart home and dual-income families, and highlight our findings from using this method.