Cases are widely used in professional education to engage learners with examples of real world practices. Collaboration in case-based learning can add to the authenticity of the experience by encouraging learners to synthesize multiple perspectives. In this paper, we present some of our experiences in collaborative case-based learning in the context of a usability engineering (UE) course. The work reported here is part of an ongoing project designing UE cases and learning activities that use them; more recently we have begun to explore the role of collaborative activities and tools in case-based learning. We describe the activities that were developed and fielded in two different UE courses, and two collaborative tools created to support these activities - a collaborative case browser and a collaborative case builder. Students were positive about both types of collaborative activities and offered suggestions for how to enhance effectiveness in the future.