Google Cloud Connect for Microsoft Office is essentially a plugin for Windows versions of the productivity suit (2003, 2007, 2010).

The plugin syncs your work through Google's cloud, so everyone can contribute to the same version of a file at the same time.

XeniT made a prototype for such functionality in 2008 for an IWT market study. Vision was right, Google has a bit more funding :-).

See the whole presentation in this video: