Hylke Bons wrote a very nice git-based Dropbox alternative with focus on collaboration called SparkleShare (http://www.sparkleshare.org http://www.sparkleshare.

Hylke Bons wrote a very nice git-based Dropbox alternative with focus on collaboration called SparkleShare (http://www.sparkleshare.org http://www.sparkleshare.org). It's still in beta state but a few members of the GNOME design team are already using it to collaborate.