In this paper, we present a new method for organizing collaborative work. This method is based on the concept of “activities,” defined here as high-level structured representations of the people, artifacts, and processes involved in work and their relationships. We show how users and developers can leverage this representation to enhance productivity, collaboration, and business applications. Central to our vision is an interface to activity data which is lightweight, based on Web Services, and enables activities to be easily integrated into the applications and tools people already use. We describe the Wax system for activity management, which implements our model of unified activity using both semantic Web and REST/XML (Representational State Transfer/Extensible Markup Language) approaches. We describe several user interfaces that let users interact with activity data, and we discuss our experiences using the Wax system for two case studies that involve coordinating a large event and managing accommodations for new employees.