Personal cloud services such as Dropbox are used increasingly to support collaborative work, even though they typically have poor support for tracking files and users' activities and collaborators often rely on other communication channels to be notified of changes. We present a meta-cloud storage service, MUBox, that, independent of a particular cloud storage service, provides improved support for collaboration. First, users can switch to activity views that list user activities rather than files, which is an example of an increasingly available feature in popular cloud storage clients. Second, MUBox introduces multi-user aware folder views that embed information on the last changes performed by collaborators. These folder views are enhanced based on a new concept of shadow files which act as placeholders for files that have been moved or renamed. A user study (N=16) with realistic folder exploration tasks shows that activity views have a significant effect on the accuracy and confidence of users in workspace awareness tasks, while shadow files significantly improve the speed, accuracy and confidence of users in traceability tasks. We describe how existing services could implement these features as well as a new concept for voting on changes to shared folders that could improve asynchronous collaboration.