SpiderOak provides an easy, secure and consolidated free online backup, sync, sharing, access & storage solution for Windows, Mac OS X, and Linux (Ubuntu, Debian & Fedora)
Conduit is a synchronization application for GNOME. It allows you to synchronize your files, photos, emails, contacts, notes, calendar data and any other type of personal information and synchronize that data with another computer, an online service, or even another electronic device.
J. Broekstra, A. Kampman, and F. van Harmelen. Proceedings of the first International Semantic Web
Conference (ISWC 2002), 2342, page 54--68. Sardinia, Italy, Springer Verlag, Heidelberg Germany, (June 2002)See also http://www.openrdf.org/.