Activity-based computing (ABC) is a conceptual and technological framework for designing interactive systems that offers a better mapping between the activities people conduct and the digital entities they use. In ABC, rather than interacting directly with lower-level technical entities like files, folder, documents, etc., users are able to interact with 'activities' which encapsulate files and other low-level resources. In ABC an 'activity' can be shared between collaborating users and can be accessed on different devices. As such, ABC is a framework that suits the requirements of designing interactive spaces. This chapter provides an overview of ABC with a special focus on its support for collaboration ('Activity Sharing') and multiple devices ('Activity Roaming'). These ABC concepts are illustrated as implemented in two different interactive spaces technologies; ReticularSpaces [3] and the eLabBench [21, 22]. The chapter discusses the benefits of activity-based collaboration support for these interactive spaces, while also discussing limitations and challenges to be addressed in further research.