Earth allows you to find files across a large network of machines and track disk usage in real time. It consists of a daemon that indexes filesystems in real time and reports all the changes back to a central database. This can then be queried through a simple, yet powerful, web interface. Think of it like Spotlight or Beagle but operating system independent with a central database for multiple machines with a web application that allows novel ways of exploring your data.
S. Ries, J. Kangasharju, and M. Mühlhäuser. On the Move to Meaningful Internet Systems 2006: OTM 2006 Workshops, volume 4277 of Lecture Notes in Computer Science, page 894--903. Berlin/Heidelberg, Springer, (2006)